It is well recognized that regulatory T cells (Tregs) are immunosuppressive, by which they prevent systemic autoimmunity throughout life. Beyond this stereotypical function, however, a growing body of evidence demonstrates that Tregs in distinct tissues, including the visceral adipose tissue, dystrophic muscle, the flu-infected lung, and wounded skin can acquire unique functions directed by their local environment. Tregs in these tissues can employ a wide variety of mechanisms to accumulate and acquire tissue-specific function, including conversion from conventional T cells, canonical T cell receptor (TCR)-dependent expansion and non-canonical, TCR-independent, cytokine-dependent expansion. Intriguingly, the niche-specific function of tissue Tregs can be independent of, and mutually exclusive of, their immunosuppressive capacity. Together, this recent literature reveals that Tregs can accumulate in discrete tissue sites through non-canonical mechanisms, and in response to niche-specific cues can acquire distinct functions, which distinguish them from their peripheral, lymphoid Treg counterparts. Other tissue Treg populations remain to be identified and characterized. Moreover, it is unknown whether other tissue Tregs rely on non-canonical mechanisms of accumulation, and exhibit functions distinct from the typical Treg immunosuppressive role. Tregs are known to accumulate in the CNS during infection, injury and inflammation. The CNS is an organ with distinctive architecture that maintains a regulated interaction with the peripheral immune system due to its critical function and poor regenerative capacity. While it is known that Tregs broadly protect against excessive tissue pathology in the diseased CNS, the origin, localization, function, mechanism of accumulation, and gene signature of CNS-infiltrating Tregs have not been studied, likely due to the challenge of isolating these rare cells and distinguishing them from circulating cells left over after perfusion. Here, we establish a safe model of CNS infection using encephalomyocarditis virus and employ a series of methods to locate, monitor and isolate CNS-infiltrating Tregs free from contamination from the circulation. We show that a distinct population of thymus-derived Tregs accumulates within the cerebrospinal fluid (CSF) of the EMCV-infected CNS, independently of lymph node priming. Tregs function in this unique niche to limit excessive tissue pathology. While CNS Tregs maintain expression of core Treg signature genes, including FoxP3, their global transcriptome is more similar to that of conventional T cells (Tcons) harvested from the infected CNS than to that of peripheral Tregs. Bioinformatics analysis reveals that genes shared by CNS Tcons and CNS Tregs are also shared by Tregs and Tcons from injured muscle and from the visceral adipose tissue of aged mice, indicating that tissue inflammation and injury, rather than viral infection per se, contribute to CNS Treg accumulation, function and phenotype. Additionally, we observe that CNS Treg accumulation during infection is associated with a simultaneous increase in meningeal/choroid plexus dendritic cells (m/chDCs), which are professional antigen presenting cells that localize to the gates of the CNS. Splenic cDC and peripheral lymphoid Treg homeostasis are linked, and both populations can be artificially increased by treatment with the DC-poietin and adjuvant, Ftlt3L. Therefore, we hypothesized that CNS Tregs and m/chDCs may also be linked and could also be manipulated by Flt3L treatment. Indeed, treatment with Flt3L in conjunction with EMCV infection results in enhanced CNS Treg and m/chDC accumulation, independent of Flt3 receptor expression on Tregs. In an effort to determine if dendritic cells mediate CNS Treg increase during infection, we turned to a DC-ablative mouse model in which all CD11c-expressing cells express the catalytic subunit of diphtheria toxin and are depleted. Surprisingly, while splenic cDCs are completely abrogated in these mice, a portion of m/chDCs persists, unaffected. Moreover, CNS Tregs accumulate normally in these mice during infection. This data suggests an unappreciated heterogeneity in m/chDCs, and indicates that those that remain unaffected in these mice may mediate CNS Treg accumulation during infection. While characterizing m/chDC heterogeneity, we found that m/chDCs comprise three distinct subsets with unknown potential. Whereas m/chDCs were previously considered to be a homogeneous, CD45hiB220-CD11c+MHCII+ population, we have found them to contain three subsets, distinguishable by IRF8 and FcR-γ expression. This finding paves the way for further study of the origin, localization, and division of labor between these three m/chDC subsets. In summary, our studies clarify the distinct compartmentalization, lymph node-independent accumulation, and inflammation-associated gene signature of CNS Tregs. Most importantly, these findings have implications for neuro-immune cross-talk, particularly at the interface of the CSF and brain parenchyma. That is, neural progenitors extend their apical domains into the CSF of the ventricles, and therefore may be subject to regulation by CSF-borne Tregs. Further, while many studies have focused on the differences between tissue Treg subsets, we find a core set of genes expressed by CNS Tregs, injured muscle Tregs and VAT Tregs. This data suggests that common mechanisms may be used for therapeutic manipulation of these cells.

A sepse é uma síndrome de resposta inflamatória sistêmica decorrente de um processo infeccioso, a qual acarreta alta taxa de mortalidade. Relatos da literatura tem demonstrado que pacientes e animais de experimentação que sobrevivem à sepse desenvolvem quadro de imunossupressão tardia, o qual contribui com a maior sucetibilidade destes a infecções secundárias. Nosso grupo demonstrou que as células T reguladoras (Tregs) participam ativamente do desenvolvimento desta imunossupressão. O Fator de Necrose Tumoral (TNF) é uma citocina pleotrópica responsável por diversas funções durante a resposta inflamatória, apresentando dois receptores responsáveis pelas suas atividades: o TNFR1 e o TNFR2. Foi demonstrando que o TNF exerce um importante papel na atividade de Tregs, induzindo a proliferação, estabilização do fenótipo e aumentando sua atividade imunossupressora, sugerindo que tais atividades sejam atribuidas ao TNFR2. Desta forma, nosso objetivo foi avaliar a participação dos receptores de TNF no desenvolvimento da imunossupressão pós-sepse. Para isso animais WT, TNFR1-/- e TNFR1/2 -/- foram submetidos à sepse grave, induzida por CLP e tratados com um suporte básico (reposição hidríca e antibioticoterapia). Inicialmente avaliamos a participação dos receptores de TNF na fase aguda da sepse. Demonstramos que nesta fase os receptores de TNF, principalmente TNFR1, apresentam um papel prejudicial na migração de neutrófilos, no controle do processo infeccioso e nas lesões de orgãos decorrentes da sepse. Posteriormente, os animais sobreviventes foram infectados com um dose subletal de L. pneumophila i.n 15 dias após a CLP. Avaliamos a participação dos receptores TNF na sucetibilidade à infecção secundária induzida por L. pneumophila em animais sobreviventes à sepse. Observamos que animais TNFR1-/- sobreviventes à sepse são mais suscetíveis, ao passo que animais TNFR1/2-/- sobreviventes à sepse são resitentes à infecção secundária em relação aos animais WT sobreviventes à sepse. Avaliamos então, a expansão de Tregs no baço destes animais sobreviventes à sepse e, observamos que animais TNFR1-/- apresentam aumento da expansão de Tregs, ao passo que os animais TNFR1/2-/- não apresentaram expansão de Tregs comparados ao WT. Observamos também que as Tregs apresentam maior densidade de receptores de TNF do que as células T convencionais e, que durante a sepse ocorre aumento da densidade destes receptores nas Tregs. Sugerimos então que possivelmente o TNFR1 seja um regulador negativo, enquanto o TNFR2 possa assumir um papel na regulação positiva na expansão de Tregs após a sepse, durante o desenvolvimento da imunossupressão. / Sepsis is a systemic inflammatory response syndrome resulting from infectious process, resulting in high mortality rate. It has been shown that septic mice and patients that survived from sepsis develop a late immunosuppression, which contributes to greater susceptibility to these secondary infections. Our group has shown that regulatory T cells (Tregs) actively participate in the development of this immunosuppression. The Tumor Necrosis Factor (TNF) is pleiotropic cytokine responsible for several processes in the inflammatory response. Two receptors are responsible for the various activities of TNF: TNFR1 and TNFR2. It have shown that TNF plays an important role in the activity of Tregs, inducing proliferation, stabilization of phenotype and increasing their immunosuppressive activity. The authors also suggested that these activities are TNFR2-mediated. Thus, our objective was to evaluate the role of TNF receptors in the acute phase of sepsis and also in the development of immunosuppression post-sepsis. For that, TNFR1-/ -, TNFR1/2 -/ - and WT mice were underwent to severe sepsis induced by CLP and treatment with basic support (hydration and antibiotics). Initially we evaluated the participation of TNF receptors in the acute phase of sepsis. We suggest that at this stage the TNF receptor, TNFR1 mainly exert a deleterious role in the migration of neutrophils in control of the infectious process and the tissue damage resulting from sepsis. In addition, the survivors from the septic event were intranasaly infected with L. pneumophila in the 15th day after sepsis induction. We evaluated the participation of these receptors in susceptibility to secondary infection induced by L. pneumophila in survivors from sepsis. Comparing the animals that survived from sepsis, we observed that TNFR1/2-/- , like WT mice, are not susceptible to the secondary infection, while TNFR1-/- survivors are more susceptible to it. We also observed that TNFR1-/ - animals show increased expansion of Tregs in the spleen, different of TNFR1/2-/- mice, that did not show expansion of Tregs compared to WT. We also observed Tregs have a higher density of receptors for TNF than conventional T cells, whereas during sepsis occurs increased expression of this receptor in Tregs. Altogether, the results suggest that TNFR1 is a negative regulator, whereas TNFR2 may play a role in the upregulation during expansion of Tregs, in development of sepsis-induced imunossupression.

PhD / Introduction Kidney transplantation confers both survival and quality of life advantages over dialysis for most people with end-stage kidney disease (ESKD). The mortality rate on dialysis is 10-15% per year, compared with 2-4% per year post-transplantation. Short-term graft survival is related to control of the acute rejection process, requiring on-going immunosuppression. Most current immunosuppressive algorithms include one of the calcineurin inhibitors (CNI: cyclosporin or tacrolimus), an anti-metabolite (azathioprine or mycophenolate) and corticosteroids, with or without antibody induction agents (Ab) given briefly peri-transplantation. Despite this approach, between 15-35% of recipients undergo treatment for an episode of acute rejection (AR) within one year of transplantation. Transplantation is not without risk, and relative mortality rates for kidney recipients after the first post-transplant year remain 4-6 times that of the general population. Longer-term transplant and recipient survival are related to control of chronic allograft nephropathy (rooted in the interplay of AR, non-immunological factors, and the chronic nephrotoxicity of CNI) and limitation of the complications of chronic ESKD and long-term immunosuppression: cardiovascular disease, cancer and infection, which are responsible for 22%, 39% and 21% of deaths respectively. This thesis is presented as published works on the theme of immunosuppression and cancer after kidney transplantation. The work presented in the first chapters of this thesis has striven to identify, evaluate, synthesise and distil the entirety of evidence available of new and established immunosuppressive drug agents through systematic review of randomised trial data, with particular emphasis on quantifying harms of treatment. The final chapters use inception cohort data from the Australian and New Zealand Dialysis and Transplant Registry (ANZDATA), which is first validated then used to explore the risk of cancer in more detail than was possible from trial data alone. Interleukin 2 receptor antagonists Interleukin-2 receptor antagonists (IL2Ra, commercially available as basiliximab and daclizumab) are humanised or chimeric IgG monoclonal antibodies to the alpha subunit of the IL2 receptor present only on activated T lymphocytes, and the rationale for their use has been as induction agents peri-transplantation. Introduced in the mid-1990s, IL2Ra use has increased globally, and by 2003 38% of new kidney transplant recipients in the United States and 25% in Australasia received an IL2Ra. This study aimed to systematically identify and synthesise the evidence of effects of IL2Ra as an addition to standard therapy, or as an alternative to other induction agents. We identified 117 reports from 38 randomised trials involving 4893 participants. Where IL2Ra were compared with placebo (17 trials; 2786 patients), graft loss was not different at one (Relative Risk -RR 0.84; 0.64 to 1.10) or 3 years (RR 1.08; 0.71 to1.64). AR was reduced at 6 months (RR 0.66; 0.59 to 0.74) and at 1 year (RR 0.66; 0.59 to 0.74) but cytomegalovirus (CMV) disease (RR 0.82; CI 0.65 to 1.03) and malignancy (RR 0.67; 0.33 to1.36) were not different. Where IL2Ra were compared with other antibody therapy no significant differences in treatment effects were demonstrated, but IL2Ra had significantly fewer side effects. Given a 40% risk of rejection, 7 patients would need treatment with IL2Ra in addition to standard therapy, to prevent 1 patient having rejection, with no definite improvement in graft or patient survival. There was no apparent difference between basiliximab and daclizumab. Tacrolimus versus cyclosporin for primary immunosuppression There are pronounced global differences in CNI use; 63% of new kidney transplant recipients in the USA but only 22% in Australia receive tacrolimus as part of the initial immunosuppressive regimen. The side effects of CNI differ: tacrolimus is associated more with diabetes and neurotoxicity, but less with hypertension and dyslipidaemia than cyclosporin, with uncertainty about equivalence of nephrotoxicity or how these relate to patient and graft survival, or impact on patient compliance and quality of life. This study aimed to systematically review and synthesise the positive and negative effects of tacrolimus and cyclosporin as initial therapy for renal transplant recipients. We identified 123 reports from 30 randomised trials involving 4102 participants. At 6 months graft loss was reduced in tacrolimus-treated recipients (RR 0•56; 0•36 to 0•86), and this effect persisted for 3 years. The relative reduction in graft loss with tacrolimus diminished with higher levels of tacrolimus (P=0.04), but did not vary with cyclosporin formulation (P=0.97) or cyclosporin level (P=0.38). At 1 year, tacrolimus patients suffered less AR (RR 0•69; 0•60 to 0•79), and less steroid-resistant AR (RR 0•49; 0•37 to 0•64), but more insulin-requiring diabetes (RR 1•86; 1•11 to 3•09), tremor, headache, diarrhoea, dyspepsia and vomiting. The relative excess in diabetes increased with higher levels of tacrolimus (P=0.003). Cyclosporin-treated recipients experienced significantly more constipation and cosmetic side-effects. We demonstrated no differences in infection or malignancy. Treating 100 recipients with tacrolimus instead of cyclosporin for the 1st year post-transplantation avoids 12 suffering acute rejection and 2 losing their graft but causes an extra 5 to become insulin dependent diabetics, thus optimal drug choice may vary among patients. Target of rapamycin inhibitors for primary immunosuppression Target of rapamycin inhibitors (TOR-I) are among the newest immunosuppressive agents and have a novel mode of action but uncertain clinical role. Sirolimus is a macrocyclic lactone antibiotic and everolimus is a derivative of sirolimus. Both prevent DNA synthesis resulting in arrest of the cell cycle. Animal models suggested TOR-I would provide synergistic immunosuppression when combined with CNI, but early clinical studies demonstrated synergistic nephrotoxicity. Since then diverse trials have explored strategies that avoid this interaction and investigated other potential benefits. The aim of this study was to systematically identify and synthesise available evidence of sirolimus and everolimus when used in initial immunosuppressive regimens for kidney recipients. We identified 142 reports from 33 randomised trials involving 7114 participants, with TOR-I evaluated in four different primary immunosuppressive algorithms: as replacement for CNI, as replacement for antimetabolites, in combination with CNI at low and high dose, and with variable dose of CNI. When TOR-I replaced CNI (8 trials, 750 participants), there was no difference in AR (RR 1.03; 0.74 to 1.44), but creatinine was lower (WMD -18.31 umol/l; -30.96 to -5.67), and bone marrow more suppressed (leucopoenia RR 2.02; 1.12 to 3.66, thrombocytopenia RR 6.97; 2.97 to 16.36, anaemia RR 1.67; 1.27 to 2.20). When TOR-I replaced antimetabolites (11 trials, 3966 participants), AR and CMV were reduced (RR 0.84; 0.71 to 0.99 and RR 0.49; 0.37 to 0.65) but hypercholesterolaemia was increased (RR 1.65; 1.32 to 2.06). When low was compared to high-dose TOR-I, with equal CNI dose (10 trials, 3175 participants), AR was increased (RR 1.23; 1.06 to 1.43) but GFR higher (WMD 4.27 ml/min; 1.12 to 7.41). When low-dose TOR-I and standard-dose CNI were compared to higher-dose TOR-I and reduced CNI AR was reduced (RR 0.67; 0.52 to 0.88), but GFR also reduced (WMD -9.46 ml/min; -12.16 to -6.76). There was no significant difference in mortality, graft loss or malignancy risk demonstrated for TOR-I in any comparison. Generally surrogate endpoints for graft survival favoured TOR-I (lower risk of acute rejection and higher GFR) and surrogate endpoints for patient outcomes were worsened by TOR-I (bone marrow suppression, lipid disturbance). Long-term hard-endpoint data from methodologically robust randomised trials are still needed. Monoclonal and polyclonal antibody therapy for treating acute rejection Strategies for treating AR include pulsed steroids, an antibody (Ab) preparation, the alteration of background immunosuppression, or combinations of these options. In 2002, in the USA 61.4% of patients with AR received steroids, 20.4% received Ab and 18.2% received both. The Ab available for AR are not new: horse and rabbit derived polyclonal antibodies (ATG and ALG) have been used for 35 years, and a mouse monoclonal antibody (muromonab-CD3) became available in the late 1980s. These preparations remove the functional T-cell population from circulation, producing powerful saturation immunosuppression which is useful for AR but which may be complicated by immediate toxicity and higher rates of infection and malignancy. The aim of this study was to systematically evaluate and synthesise all evidence available to clinicians for treating AR in kidney recipients. We identified 49 reports from 21 randomised trials involving 1394 participants. Outcome measures were inconsistent and incompletely defined across trials. Fourteen trials (965 patients) compared therapies for 1st AR episodes (8 Ab versus steroid, 2 Ab versus another Ab, 4 other comparisons). In treating first rejection, Ab was better than steroid in reversing AR (RR 0.57; CI 0.38 to 0.87) and preventing graft loss (RR 0.74; CI 0.58 to 0.95) but there was no difference in preventing subsequent rejection (RR 0.67; CI 0.43 to 1.04) or death (RR 1.16; CI 0.57 to 2.33) at 1 year. Seven trials (422 patients) investigated Ab treatment of steroid-resistant rejection (4 Ab vs another Ab, 1 different doses Ab, 1 different formulation Ab, 2 other comparisons). There was no benefit of muromonab-CD3 over ATG or ALG in reversing rejection (RR 1.32; CI 0.33 to 5.28), preventing subsequent rejection (RR 0.99; CI 0.61 to 1.59), graft loss (RR 1.80; CI 0.29 to 11.23) or death (RR 0.39; CI 0.09 to 1.65). Given the clinical problem caused by AR, comparable data are sparse, and clinically important differences in outcomes between widely used interventions have not been excluded. Standardised reproducible outcome criteria are needed. Validity of cancer data in an end stage kidney disease registry Registries vary in whether the data they collect are given voluntarily or as a requirement of law, the completeness of population coverage, the breadth of data collected and whether data are assembled directly or indirectly through linkage to other databases. Data quality is crucial but difficult to measure objectively. Formal audit of ANZDATA cancer records has not previously taken place. The aim of this study was to assess agreement of records of incident cancer diagnoses held in ANZDATA (voluntary reporting system) with those reported under statute to the New South Wales (NSW) state Central Cancer Registry (CCR), to explore the strengths and weaknesses of both reporting systems, and to measure the impact of any disagreement on results of cancer analyses. From 1980-2001, 9453 residents received dialysis or transplantation in NSW. Records from ANZDATA registrants were linked to CCR using probabilistic matching and agreement between registries for patients with 1 or more cancers, all cancers and site-specific cancer was estimated using the kappa-statistic (κ). ANZDATA recorded 867 cancers in 779 (8.2%) registrants; CCR 867 cancers in 788 (8.3%), with κ =0.76. ANZDATA had sensitivity 77.3% (CI 74.2 to 80.2), specificity 98.1% (CI 97.7 to 98.3) if CCR records were regarded as the reference standard. Agreement was similar for diagnoses whilst receiving dialysis (κ =0.78) or after transplantation (κ =0.79), but varied by cancer type. Melanoma (κ =0.61) and myeloma (κ =0.47) were less good; lymphoma (κ =0.80), leukaemia (κ =0.86) and breast cancer (κ =0.85) were very good. Artefact accounted for 20.8% non-concordance but error and misclassification did occur in both registries. Cancer risk did not differ in any important way whether estimated using ANZDATA or CCR records. Quality of cancer records in ANZDATA are high, differences largely explicable, and seem unlikely to alter results of analyses. Risk of cancer after kidney transplantation Existing data on the magnitude of excess risk of cancer across different kidney recipient groups are sparse. Quantifying an individual transplant candidate’s cancer risk informs both pre-transplant counselling, treatment decisions and has implications for monitoring, screening and follow-up after transplantation. The aims of this study were firstly to establish the risk of cancer in the post-transplant population compared to that experienced by the general population, and secondly to quantify how excess risk varied within the transplanted population, seeking to establish meaningful absolute risk estimates for post-transplant cancer based on unalterable recipient characteristics known a priori at the time of transplantation. 15,183 residents of Australia and New Zealand had a transplant between 1963 and 2004, and were followed for a median of 7.2 years (130,186 person-years), with 1642 (10.8%) developing cancer. Overall, kidney recipients had 3 times the cancer risk, with risk inversely related to age (Standardised Incidence Ratio of 15 to 30 in children reducing to 2 in people > 65 years). Female recipients aged 25 -29 had rates of cancer (779.2/100,000) equivalent to women aged 55 - 59 from the general population. The risk pattern of lymphoma, colorectal and breast cancer was similar to the overall age trend, melanoma showed less variability across ages and prostate cancer showed no risk increase. Within the transplanted population cancer risk was affected by age differently for each sex (P=0.007), and was elevated for recipients with prior non-skin malignancy (Hazard Ratio: HR 1.40; 1.03 to 1.89), of white race (HR 1.36; 1.12 to 1.89), but reduced for those with diabetic ESKD (HR 0.67; 0.50 to 0.89) Rates of cancer in kidney recipients were similar to non-transplanted people 20 -30 years older, but risk differed across patient groups. Men aged 45 - 54 at transplantation with graft function at 10 years had a risk of cancer that varied from 1 in 13 (non-white, diabetic ESKD, no prior cancer) to 1 in 5 (white, prior cancer, ESKD from other causes).

The transmembrane isoform of mucin 1 (MUC1/TM) is a well recognized tumor antigen, contributing to tumorigenesis and immune evasion. While MUC1/TM has been correlated with malignancy, it appears that a secreted splice variant of MUC1 (MUC1/sec) has antitumor properties and prevents tumor development. It was discovered that MUC1/sec expressing tumor cells (DA-3/sec) have a significant reduction in expression of urokinase plasminogen activator (uPA) relative to the parental tumor line, and tumor cells expressing MUC1/TM (DA-3/TM). The serine protease uPA, has been found to be involved in growth promoting signaling, angiogenesis, and induction of matrix remodeling leading to metastasis. Furthermore, the tumor suppressive and interferon responsive Stat1 transcription factor is dramatically upregulated in DA-3/sec cells. In addition, treatment of various murine and human cell lines with conditioned media containing MUC1/sec results in up-regulation of Stat1. DA-3/sec tumor cells are also sensitized to the anti-proliferative effects of IFN-g. Furthermore, transfection of the Stat1 gene into DA-3 tumor cells leads to a downregulation of uPA, and delays tumor progression. Since myeloid-derived suppressor cells (MDSC) play a critical role in tumor-induced immunosuppression, we investigated their recruitment by DA-3/sec and DA-3/TM cells. DA-3/sec tumor cells recruit dramatically lower levels of MDSC, relative to DA-3/TM cells. Since MUC1/sec down-regulates tumor expression of uPA, its potential role in MDSC recruitment was investigated. Tumor-derived uPA is capable of recruiting MDSC, and correlates with tumor development. In addition to diminishing recruitment of MDSC, the effect of MUC1/sec on MDSC suppressive mechanisms was investigated. MUC1/sec, or its unique immunoenhancing peptide (IEP), is capable of blocking expression of arginase 1 and production of reactive oxygen species (ROS) in MDSC, implicated in the suppression of T cells. These findings demonstrate a new mechanism of MDSC recruitment, and provide evidence that MUC1/sec has antitumor properties affecting both tumor cells and MDSC. Furthermore, it was discovered that MDSC home to the liver in addition to the tumor, bone marrow, blood, and spleen of tumor bearers, as previously described. The liver is thus an organ where MDSC accumulate and can contribute to immunosuppression directly and indirectly, via interactions with a variety of immune cells.

The organic mercury compound ethylmercurithiosalicylate (thimerosal), an antiseptic and a preservative, has recently raised public health concern due to its presence in vaccines globally. Thimerosal dissociates in the body to thiosalicylate and ethyl mercury (EtHg), which is partly converted to inorganic mercuric mercury (Hg2+). The immunosuppressive, immunostimulatory, and de novo autoimmunogen effect of thimerosal in mice, as well as the accelerating/aggravating effect on spontaneous systemic autoimmunity including dose-response aspects were the subject of this thesis. Thimerosal perorally (590 μg Hg/kg body weight (bw)/day) to genetically susceptible (H-2s) mice caused immunosuppression during the first week with reduction of the total number of splenocytes, T- and B-cells. The suppression lasted 2 weeks for CD4+ cells, but was superseded by a strong immunostimulation/proliferation including T- as well as B-cells, and polyclonal B-cell activation (PBA). Antinuclear antibodies targeting the 34-kDa nucleolar protein fibrillarin (AFA) appeared after 10 days, followed by renal mesangial and systemic vessel wall immune-complex (IC) deposits. The Lowest Observed Adverse Effect Level (LOAEL) was in the order AFA = glomerular and splenic vessel wall deposits < hyperimmunoglobulinemia < PBA. The LOAEL for AFA was 118 μg Hg/kg bw/day. The LOAEL for the different parameters of this thimerosal-induced systemic autoimmune condition (HgIA) was 3-11-fold higher compared with HgIA induced by HgCl2. The thimerosal-induced HgIA shared with HgCl2 a significant dose-response relationship, and requirement for: T-cells, the costimulatory factor CD28, the IFN-γ/IFN-γ-receptor pathway,but not IL-4. The mRNA expression in lymph nodes of IL-2, IFN-γ, IL-4, and IL-15 was significantly increased but not delayed compared with HgCl2. Treatment with the ubiquitous organic Hg compound methyl Hg using equimolar doses of Hg (533 μg Hg/kg bw/day) caused a transient immunosuppression, followed by a weak immunostimulation and AFA. The IgG AFA isotypes induced by the organic Hg compounds MeHg and EtHg were stable and dominated by a Th1-like pattern over a broad time- and dose range. Treatment with inorganic HgCl2 caused a dose- and time-dependent pattern of IgG AFA isotypes. Low doses favored a Th1-like pattern, a high dose a balanced or Th2-like pattern. Middle-range doses showed initially a Th1-like pattern which gradually evolved into a balanced or Th2-like pattern. The qualitative difference in IgG AFA isotypes between organic and inorganic Hg may be due to differences in activation and/or suppression of T-helper cell subsets or factors influencing the Th1/Th2-function. Speciation of the renal Hg2+ concentration and comparison with the threshold dose for induction of AFA by HgCl2 showed that even with the lowest doses of thimerosal and MeHg used in this thesis, the AFA response might from a dose threshold point of view have been caused by conversion of the organic Hg species to Hg2+. Primary treatment with inorganic Hg (HgCl2) accelerates/aggravates murine systemic autoimmunity, both spontaneous (genetic) and induced by other means. This capacity was assessed for thimerosal over a broad dose range using the (NZB X NZW)F1 hybrid mouse model. Significantly increased antinuclear antibodies (ANA) was seen after 4-7 weeks treatment (LOAEL 147 μg Hg/kg bw/day), and the response was dose-dependent up to 13 weeks. Renal mesangial and systemic vessel walls deposits similar to those in de novo HgIA were present after 7 weeks treatment. Twenty-two to 25 weeks treatment with thimerosal caused, in a dose-dependent fashion (LOAEL 295 μg Hg/kg bw/day), relocalization of the spontaneously developing glomerular IC deposits from the capillary vessel walls to the mesangium, which attenuated histological kidney damage and proteinuria, and increased survival. Thimerosal caused systemic vessel wall IC-deposits over a broad dose range: the Low Observed Adverse Effect Level (LOAEL) for renal and splenic vessel wall IC deposits was 18 and 9 μg Hg/kg bw/day, respectively. The No Observed Adverse Effect Level (NOAEL) could not be determined for the latter, since deposits were present even with the lowest dose used. Thimerosal causes in genetically susceptible mice an initial, transient immunosuppression which is superseded by a strong immunostimulation and systemic autoimmunity, sharing many characteristics with the HgIA induced by inorganic HgCl2. The IgG AFA isotype pattern is however qualitatively different, and the threshold dose substantially higher. In contrast, long-term treatment with thimerosal induces systemic vessel wall IC-deposits also using doses below those needed to induce HgIA de novo in H-2s mice.

Background: Currently, the optimal long-term therapy for end stage heart failure is heart transplantation. Cardiac allograft vasculopathy contributes to a significant number of deaths following transplantation. This vasculopathy is related to early endothelial injury sustained at the time of organ transplantation and to persistent endothelial injury as a result of cytotoxic immunosuppression, as well as chronic rejection. Epidermal growth factor-like domain 7 (Egfl7), is expressed in endothelial cells upon arterial injury and may have a role in maintaining vascular endothelial integrity and regeneration following injury. Similarly, novel pharmacologic agents such as Bosentan, an endothelin-1 antagonist, and Cilostazol, a phosphodiesterase 3 inhibitor, have been demonstrated to attenuate calcineurin inhibition induced endothelial dysfunction and neointimal hyperplasia, respectively. We hypothesized that, 1) Egfl7 will attenuate endothelial activation, cell adhesion molecule expression and neutrophil adhesion following simulated ischemia-reperfusion injury or exposure to calcineurin inhibition and that, 2) Bosentan and Cilostazol will inhibit neointimal hyperplasia following endothelial injury in a mouse model of vascular injury. Methods: Human coronary artery endothelial cells were subjected to hypoxia-reoxygenation injury or the calcineurin inhibitors Cyclosporine A and Tacrolimus to examine the effects of Egfl7 on these injury mechanisms. Cell adhesion molecule expression, neutrophil adhesion to endothelial cells, and NF-κB activation were measured. Cell adhesion molecule and Egfl7 expression were also examined in a mouse model of neointimal. This model was used to examine the effects of Bosentan and Cilostazol on neointimal hyperplasia. Results: Egfl7 had potent anti-inflammatory properties including inhibition of NF-κB pathway activation, ICAM-1 expression and neutrophil adhesion to injured endothelium. Within vessels exhibiting neointimal hyperplasia, Egfl7 was expressed in regions lacking ICAM-1 expression. Both cilostazol and bosentan attenuated neointimal hyperplasia in isolation as well as during co-treatment with CNI therapies. Conclusions: Egfl7 is an endothelial protective signaling protein with anti-inflammatory properties effective against simulated ischemia-reperfusion injury and calcineurin inhibition mediated injury. Cilostazol and Bosentan are pharmacologic strategies demonstrating efficacy against the development of neointimal hyperplasia. These observations provide a novel therapeutic target and strategies that may be relevant to endothelial protection and prevention of cardiac allograft vasculopathy following heart transplantation.

Background: Currently, the optimal long-term therapy for end stage heart failure is heart transplantation. Cardiac allograft vasculopathy contributes to a significant number of deaths following transplantation. This vasculopathy is related to early endothelial injury sustained at the time of organ transplantation and to persistent endothelial injury as a result of cytotoxic immunosuppression, as well as chronic rejection. Epidermal growth factor-like domain 7 (Egfl7), is expressed in endothelial cells upon arterial injury and may have a role in maintaining vascular endothelial integrity and regeneration following injury. Similarly, novel pharmacologic agents such as Bosentan, an endothelin-1 antagonist, and Cilostazol, a phosphodiesterase 3 inhibitor, have been demonstrated to attenuate calcineurin inhibition induced endothelial dysfunction and neointimal hyperplasia, respectively. We hypothesized that, 1) Egfl7 will attenuate endothelial activation, cell adhesion molecule expression and neutrophil adhesion following simulated ischemia-reperfusion injury or exposure to calcineurin inhibition and that, 2) Bosentan and Cilostazol will inhibit neointimal hyperplasia following endothelial injury in a mouse model of vascular injury. Methods: Human coronary artery endothelial cells were subjected to hypoxia-reoxygenation injury or the calcineurin inhibitors Cyclosporine A and Tacrolimus to examine the effects of Egfl7 on these injury mechanisms. Cell adhesion molecule expression, neutrophil adhesion to endothelial cells, and NF-κB activation were measured. Cell adhesion molecule and Egfl7 expression were also examined in a mouse model of neointimal. This model was used to examine the effects of Bosentan and Cilostazol on neointimal hyperplasia. Results: Egfl7 had potent anti-inflammatory properties including inhibition of NF-κB pathway activation, ICAM-1 expression and neutrophil adhesion to injured endothelium. Within vessels exhibiting neointimal hyperplasia, Egfl7 was expressed in regions lacking ICAM-1 expression. Both cilostazol and bosentan attenuated neointimal hyperplasia in isolation as well as during co-treatment with CNI therapies. Conclusions: Egfl7 is an endothelial protective signaling protein with anti-inflammatory properties effective against simulated ischemia-reperfusion injury and calcineurin inhibition mediated injury. Cilostazol and Bosentan are pharmacologic strategies demonstrating efficacy against the development of neointimal hyperplasia. These observations provide a novel therapeutic target and strategies that may be relevant to endothelial protection and prevention of cardiac allograft vasculopathy following heart transplantation.

Piperine, a pungent alkaloid found in the fruits of long and black pepper plants, has diverse physiological effects, including anti-inflammatory and anti-cancer activities. The effect of piperine on the function of T cells and endothelial cells, two important elements of inflammation, have not been examined previously and were the focus of this study. Piperine inhibited the proliferation of human endothelial cells, murine T cells, and IL-2-dependent CTLL-2 T cells, without affecting cell viability. Progression into the S phase of the cell cycle was inhibited in all three cell types. In T cells, piperine inhibited expression of the early activation marker CD25, production of IFN-?, IL-2, IL-4, and IL-17A, and the generation of cytotoxic effector cells. In endothelial cells, piperine inhibited migration and tubule formation in vitro and ex vivo, as well as breast cancer cell-induced angiogenesis in chick embryos. Piperine inhibited Akt phosphorylation in signaling pathways associated with growth factor receptors on endothelial cells, T cell receptor and CD28 on T cells, and IL-2 receptor on CTLL-2 cells. Additionally, piperine inhibited ERK1/2 and I?B phosphorylation in activated T cells, as well as STAT3, STAT5, and ERK1/2 phosphorylation in IL-2-stimulated CTLL-2 cells. However, piperine is not a broad-spectrum inhibitor of phosphorylation as it did not inhibit ZAP-70 phosphorylation in activated T cells or phosphorylation of JAK1 and JAK3 in IL-2-stimulated CTLL-2 cells. Piperine-mediated inhibition of T cell activation and IL-2 receptor signaling suppresses T cell proliferation and effector cell differentiation, suggesting possible utility in treating T cell-mediated autoimmune and chronic inflammatory conditions. Additionally, the potent anti-angiogenic activity of piperine warrants further study for the prevention of inflammation- and cancer-promoting angiogenesis.

No description available.

Background: Management of a transplant recipient involves the use of multiple immunosuppressant drugs. Currently there is no test that reflects the overall immune status of the patient. This results in under or over suppression of the immune system and consequently increases in morbidity and mortality rates. Evaluation of the proliferative response of PBMC's to a mitogen PHA by measurement of intracellular ATP was evaluated as a tool to assess the immune response in kidney transplant patients. Method: PBMC's were separated from the blood samples of healthy controls and kidney transplant patients on cyclosporine, sirolimus, and tacrolimus based regimens by density gradient centrifugation, cells were counted and incubated overnight with and without PHA. The luciferin-Iuciferase enzyme reaction which induces bioluminescence and the Turner Biosystem luminometer were used to measure intracellular ATP levels in relative light units (RLU). An A TP standard curve was generated for each test. Results: The ATP (nglml) levels measured in the transplant recipients were lower and statistically significantly different (p< 0.0001) than the healthy controls. No statistically significant difference was measured between the cycIosporine and sirolimus drug groups. Patients on tacrolimus gave a statistically significant (p<O.0001) stronger immune response than those receiving cyclosporine and sirolimus. Overall, the immune response results of kidney transplant patients were statistically significantly lower than the healthy control by 981 nglml. Linear regression analysis revealed no correlation between patient A TP (nglml) levels and therapeutic drug blood levels, immunosuppressant drug dosages, creatinine levels and white cell counts. The immune responses of patients who were diagnosed with infection or were clinically stable were characterised as low or moderate, of interest, one patient who was diagnosed with rejection was found to have a strong immune response (>501 nglml ATP). Conclusion: Future studies to determine the predictive value of the A TP assay in directing immunosuppressive therapy are required. The assay described in this study is simple, sensitive and rapid and has possible application in immunological monitoring in a variety of conditions that affects the immune system. Keywords: kidney transplantation, immunosuppression, bioluminescence, lymphocyte, Adenosine Triphosphate (A TP), Phytohemmagglutinin (PHA) / Thesis (M.Med.Sc.)-University of KwaZulu-Natal, Durban, 2008.