Introduction: Vaccination is one of the most efficient ways to prevent infectious diseases, however due to the naivety and regulation of immunity found in infants, induction of vaccine-mediated immunity is challenging. Respiratory and diarrheal diseases are major contributors to infant mortality. Additionally, Human Immunodeficiency Virus-1 (HIV) infections increase the risk of mortality. Current advances in Prevention of Mother-to-Child Transmission (PMTCT) have prevented HIV infections in almost 97% of infants being born to HIV-infected mothers. As a result there is an increasing number of HIV exposed, uninfected infants (HEU). HEU infants have a higher rate of infectious disease related mortality and morbidity compared to unexposed infants, the underling causes of these differences are still not understood. In this dissertation, responses to two childhood vaccines, live, attenuated rotaviral vaccine (Rotarix) and acellular Pertussis (aP), were analyzed in HEU infants, with specific focus on T-cell responses to Rotarix and aP, due to the current lack of published data on T-cell responses. Additionally, the influence of feeding mode, that is breast or formula feeding, was also assessed as it is well established that breast fed infants contract fewer infections compared to formula fed infants. Methods: This dissertation included infants from a larger cohort which includes three groups of infants; HIV unexposed breast fed (UBF), HIV exposed breast-fed (EBF) and HIV exposed formula fed (EFF) infants. Infants were recruited at birth and followed up until 36 weeks of age. As no Rotavirus vaccine T-cell assay was previously published, multiple techniques were utilized to attempt to optimize an assay capable of detecting Rotavirus (RV) vaccine-specific T-cell responses. To determine T-cell responses to Bordertella pertussis (BP), blood was collected from infants at each time-point and 200ul was stimulated with BP antigen in a 12-hour whole blood assay. Cells from all assays were fixed and stained for flow cytometric analysis of CD4 and CD8 T-cell responses. The markers used included live/ dead, CD3, CD4 and CD8 for identification of T-cell populations, IFNγ, IL-2 and TNFα cytokines, HLA-DR and Ki67 for activation and proliferation, and CD45RA and CD27 memory differentiation. Data analysis was then completed using Microsoft Excel, Flow.Jo V9, GraphPad prism V6, Pestle 1.7 and Spice V5.33 software packages. Results: Despite multiple attemps it was not possible to optimise an assay capable of consistently detecting Rotavirus vaccine specific responses. This was partly due to interferance from contaminating agents in the protein antigens used, and difficulty in culturing and purification of whole virus. Assessment of aP spcific CD4+ T-cell memory demonstrated an overall increase in terminally differentiated (TD) memory cells accross time. This mirrored the ontogeny of the total T cell pool which showed an overall decrease in naïve T-cell frequencies with a consequent increase in late and terminally differentiated CD4 and CD8 T-cell populations over time through the first months of life. Both total and aP specific CD4+ early differentiated (ED) memory T-cells remained unchanged over time. ED CD8+ memory T-cells peaked at week 15 in EBF infants. A similar observation was found in UBF infants but at a non-significant level. EFF infants had no significant changes in CD8+ naive, ED and late differentiated (LD) memory populations over time. Additionally all infants demonstrated high levels of Ki67 expression at D4-7, which is prior to vaccination and maintained this level of proliferation after vaccination. HEU infants had higher levels of activation compared to HU infants in the first week of life but this normalised to HU infant levels by week 7. Furthermore EFF infants had peak T-cell activation at week 7 as compared to week 15 in EBF infants. In addition HU infants had better cytokine responses than HEU infants at week 7 but similar responses at week 15 and 36. In Addition, EFF infants also had increased vaccine specific CD4+ responses at week 7 and week 36 compared to EBF infants. This was true for overall cytokine expressing CD4 T-cells and single TNFα expressing CD4+ T-cells. Disscussion: Given the important role T-cells play in the clearance of Rotavirus, it is important that an assay capable of detecting RV vaccine specific T-cell responses be developed. Furthermore, T cells play a role in providing help for antibody responses to BP and for killing of intracellular bacteria. Our findings regarding immunity to aP suggest that all infants, regardless of HIV exposure status and feeding mode, are able to mount a T cell response to aP vaccination. However the differing ontogeny of responses seen in all three groups of infants lends some insight on the complex determinants of vaccine T -cell immunogenicity. In this case, age since vaccination, HIV exposure, and feeding mode resulted in apparent changes in vaccine responses as well as T cell differetiation and activation.

Background. In some regions of Sub-Saharan Africa, up to 30% of newborns are born to mothers infected with human immunodeficiency virus (HIV). Maternal antiretroviral treatment (ART) has reduced vertical transmission to lower than 1%. Despite the success of prevention of mother-tochild transmission (PMTCT) programmes, a large number of children born to these mothers are exposed to HIV and antiretrovirals (ARVs) in utero yet remain uninfected. These individuals, known as children who are HIV-exposed and uninfected (cHEU), succumb to higher rates of disease morbidity compared to children who are HIV-unexposed (cHU) which suggests altered immunity in the cHEU. Differences in the numbers and function of cells of the innate and adaptive immune system have been documented in cHEU—though not consistently. While vaccine-induced antibody responses are robust in cHEU, data on potential cell mediated perturbations to vaccine antigens remains conflicting. This is in part due to inherent inter-cohort variation and differences in ART therapy strategies, feeding practices between cohorts and the assays used measure cellmediated responses. We leveraged two independent cohorts from Nigeria and South Africa of mother-infant pairs receiving antenatal and postnatal care all under Option B+ PMTCT. All HEU infants received pre-exposure prophylaxis for 6 weeks and the majority were exclusively breastfed until 6 months of age. We applied the same assays in both cohorts to test the hypotheses that HEU have altered T cell immunity compared to HU controls and distinct transcriptomic signatures at birth. These were tested in three distinct aims: 1) To identify transcriptional signatures at baseline that delineate cHEU from cHU 2) To compare the expression of surface marker broadly defining activated or regulatory phenotypes and the expression of intracellular markers of T cell function between cHEU and cHU over the first 9 months of life. 3) To characterise how differences in the immunising strains of Bacille Calmette-Gu'erin (BCG), the first vaccine received in these infants, impacts T cell immunity to both mycobacterial and non-mycobacterial antigens in cHEU and cHU. Methods. Two birth cohorts from Jos, Nigeria and Cape Town (CT), South Africa were recruited into this study as part of a larger parent study that aims to identify biological determinants of protection from mother-to-child transmission of HIV (Innate, Adaptive and Mucosal Immune Responses in Infants/INFANT study: HREC 285/2012). Infant blood was collected at several time points from birth to 36 weeks of life for immunological assays. Whole blood, collected at birth was preserved in PAXgene fluid for downstream messenger ribonucleic acid (mRNA) transcript analyses. Other whole blood samples were fixed and cryopreserved either directly ex vivo or after re-stimulation within 1 hour of phlebotomy with BCG, Tetanus Toxoid (TT), Bordetella pertussis (BP) antigens and Phytohemagglutinin (PHA). Multi-parameter flow cytometry was used to measure batched whole blood samples for (i) markers of T cell regulation and activation directly ex vivo, markers of T cell gut homing and proliferation—a proxy for HIV susceptibility, and (ii) vaccine-induced Th1 cytokine expression (IFN-, TNF-a, IL-2) and memory maturation. Cytokine responses were profiled for polyfunctionality by SPICE analysis and complemented by the COMPASS algorithm. Transcriptional profiling of whole blood at birth was done by RNA sequencing and differentially expressed genes were reported for absolute fold change of normalized counts were < 1.5 with FDR set at 0.05 using the DESeq2 package in R. Gene-set enrichment analysis (GSEA) was used to identify enriched or repressed gene pathways for absolute normalised effect sizes < 1.5 with FDR set at 0.05. Longitudinal analyses used a mixed effects ANOVA with time and HIV exposure as explanatory variables. Cross-sectional analyses comparing HIV exposure groups used Wilcoxon Ranked Sum Test, with p< 0.05 considered significant after multiple correction adjustment by Holm's step-down method. Results. Aim 1: A small set of DEGs were found between HEUs and HU groups at birth, 3 of which were upregulated and 12 that were downregulated. Among the upregulated genes, two are homologues of the arrestins: ARRDC4 (2.3 fold, adjusted p-adj< 0.001) and TXNIP (1.4 fold, padj< 0.001). Gene-set enrichment analysis however, showed no significant enrichment or suppression of gene pathways in HEUs. Aim 2: HIV/ARV exposure did not have an interaction effect with age (all time points) in explaining the frequencies of T cell markers ex vivo in a mixed-effects model. In cross-sectional unadjusted analyses however, trends towards increased median frequencies of markers of activation in the HEU group compared to HU controls were observed for specific ages: at birth (%CD8+HLA-DR+: 0.12 vs. 0.01, p=0.05), at week 7 (%CD8+CD25+: 0.13 vs. 0.04, p=0.01 and %CD8+HLA-DR+: 0.84 vs. 0.07, p=0.01) and at week 36 (%CD8+CD25+: 0.52 vs. 0.03, p< 0.001 and %CD8+HLA-DR+: 0.81 vs. 0.17, p=0.003). When adjusting for multiple comparisons, only CD25 expression remained significant on CD8+ T cells at week 36 (p-adj =0.04). The magnitudes of cytokine responses by T cells to vaccine antigens did not differ between HEU and HU infants however, transient differences in the polyfunctional profile of cells was observed at week 1 for mycobacterial-specific Th1 profiles in CT infants (p=0.002) by SPICE analysis. There were later differences at week 7 for BP-specific Th1 profiles in Jos infants (p=0.01) and at week 36 for BP-specific Th1 profiles in CT infants (p=0.03). The more robust COMPASS algorithm only detected a trend towards increased polyfunctional scores to BP responses in CT infants at week 36 (p=0.03). Aim 3: BCG immunising strain impacted the magnitudes and quality of responses to mycobacterial and non-mycobacterial vaccine antigens irrespective of HIV exposure status. Most significantly, at week 7, BCG-Denmark induced higher mycobacterial-specific frequencies of CD4 Th1 cytokines compared to Bulgarian (p< 0.001) and Russian strains (and (p< 0.001). BCGDenmark induced greater triple cytokine profiles to mycobacterial antigen compared to Bulgarian (p< 0.001) and Russian (p< 0.001) strains in SPICE analyses and the resulted were confirmed by COMPASS algorithm polyfunctional scores. Furthermore, BCG-Denmark significantly enhanced antigenicity to TT and BP vaccines. Conclusion. Transient differences exist in the frequencies of CD25 expressing CD8 T cells between HEU and HU groups, however other readouts of immunity suggest that in the context of effective PMTCT and exclusive breastfeeding practices, HEU infants are indistinguishable from their HIV unexposed peers.

Includes bibliographical references (leaves 150-175). / Includes abstract. / Protective immunity against mycobacterial infection requires an effective cytolytic response, in addition to an intact Type l (Th1) cytokine pathway. Natural killer (NK) cells and cytolytic T-cells (CTL) are essential components of protective immunity against tuberculosis (TB) and mediate granule-dependent killing of infected cells. Granulysin, an antimicrobial protein, and perforin, a pore-forming molecule, have been found to co-localise in the granules of these two cell types. Granulysin has been shown to be directly cytotoxic to extracellular Mycobacterium tuberculosis (M.tb) and, together with perforin, is cytolytic against intracellular mycobacteria. This project evaluated the role of these two cytolytic mediators in TB.

Young, reproductive-aged women are at highest risk of acquiring human-immunodeficiency virus (HIV). The Women's Initiative in Sexual Health (WISH) study was designed to investigate potential biological reasons for this high risk in HIV negative, South African adolescent females. Little is known about the 'normal' microbiome of this population. As such, the aim of this substudy was to quantify specific bacterial species (L. crispatus, L. jensenii, L. gasseri, L. iners, G. vaginalis and P. bivia) by quantitative real time PCR (qPCR) from adolescent female lateral vaginal wall swabs, and to assess associations between the quantities of these bacteria and bacterial vaginosis (BV) status, inflammation levels, age, hormonal contraceptive usage, and sexually transmitted infections (STIs). Samples were collected from 143 participant adolescent females in total, aged between 16 and 22 years of age, with a median of 18 years of age, from the Masiphumelele Youth Clinic in Cape Town, South Africa. Bacterial DNA was extracted from lateral vaginal wall swabs using the MoBio Powersoil® DNA Isolation Kit after enzymatic digestion. Positive bacterial reference strains were cultured in MRS buffer and Schwedler's broth, after which the DNA was extracted using the Qiagen Blood and Tissue DNA Maxi Extraction Kit. The quality and concentration of the DNA was confirmed using Qubit technology. The positive control DNA was amplified with PCR using species specific primers and the product run on an agarose gel to confirm primer specificity. The positive control DNA was serially diluted from 106 to 10-2 copies/μL to form a standard curve for absolute quantification through qPCR. Multiple steps were taken in order to optimize the qPCR experiments in terms of protocols, initial denaturation and annealing temperatures, cycle length and number, primers, and serial dilutions of the positive control DNA. The optimization for the P. bivia qPCR protocol presented the most issues, with the final quantification results being unreliable and requiring further work. Once the qPCR conditions were optimized for each bacterium; all samples, non-template control and standards were run in triplicate to quantify the number of bacterial copies per ng of DNA for each participant. The average of the three values were used as the final quantities and then used for downstream analyses. The bacterium L. crispatus, L. jensenii and L. gasseri, had median readings of 3.957 copies/ng, 1.568 copies/ng, and 17.58 copies/ng, respectively, with increased L. iners (2807 copies/ng) and G. vaginalis (8540 copies/ng). BV negative participants had increased levels of L. crispatus (p=0.0004, p=0.0002) and L. gasseri (p=0.0016, p<0.0001) in comparison to both BV intermediate and BV positive participants. L. jensenii (p<0.0001) and L. iners (p=0.0461) readings were increased in BV negative participants compared with BV positive and BV intermediate participants, respectively. BV positive participants had increased levels of G. vaginalis in comparison with both BV intermediate (p=0.0059) and BV negative (p<0.0001) adolescents. The 47 immunological factors, assessed via luminex, were categorized into high and low genital inflammation based on the unsupervised analysis by partitioning around medoids (PAM) using an R package 'cluster' with a k-value of 2. The inflammation-low group had increased levels of L. crispatus (p=0.0005), L. gasseri (p=0.033) and L. jensenii (p=0.0046) in comparison to the genital inflammation-high group. In participants with two viral STIs (Herpes Simplex Virus 2 and Human Papilloma Virus), there were increased copies/ng of G. vaginalis in comparison with participants with none (p=0.0098) or one viral STI (p=0.0324). Participants with high-risk HPV subtypes had significantly higher copy numbers of L. crispatus in comparison to the participants with low risk HPV subtypes (p=0.0181). Further, the only association demonstrated between the qPCR-based bacterial levels and the hormonal contraceptive prescribed was indicated by L. jensenii (ANOVA p=0.0222), possibly due to the low copy number readings. In conclusion, BV status, low levels of genital inflammation and the presence of two viral STIs indicate an association with bacterial copy numbers reported in this study, with increased median levels of L. iners and G. vaginalis across all adolescent participants compared to the other reported bacterial copy numbers. This indicates a possible alternate 'normal' microbiota profile of the FGT in adolescents in Masiphumelele.

Bibliography: leaves 163-191.

Rheumatoid arthritis (RA) is an autoimmune disease with systemic inflammatory features that primarily affects small peripheral joints. Type II collagen (CII), is the most abundant collagen type in joint cartilage. Antibodies against CII (anti-CII) are found in a subpopulation of RA patients. Anti-CII can form surface-bound immune complexes (IC) in inflamed joints, which might intensify joint inflammation and destruction. In this thesis I have studied the functional effects of surface-bound anti-CII–containing IC in vitro and correlated the results to clinical parameters. Anti-CII IC induced TNF-α, IL-1β and IL-8 production from monocytes via FcγRIIa. Anti-CII levels were dichotomously distributed in RA patients where a small outlier group (3.3%) with very high anti-CII levels showed in vitro induction of pro-inflammatory cytokines by anti-CII-containing IC. These patients also had a distinct phenotype with elevated laboratory signs of inflammation and increased radiological erosions at the time of diagnosis. In another in vitro model, co-cultured macrophages and RA synovial fibroblasts stimulated with anti-CII IC induced the production of matrix metalloproteinases (MMP)-1 and MMP-8, enzymes responsible for the initial cleavage of CII during cartilage degradation. This was mediated via production of TNF-α and IL-1β, and especially anti-CII IC-induced IL-1β sup-ported the production of MMP-1. The presence of anti-CII antibodies in patients with early synovitis was not predictive for future RA development. In summary, I have shown how anti-CII-containing IC may explain part of the early pathogenesis and can define a distinct clinical phenotype in RA patients with high levels of anti-CII.

Immune complexes (IC) have key pathological roles in both autoimmune and infectious diseases. In this thesis functional mechanisms behind IC-driven inflammation in rheumatic diseases and tropical infections have been studied, with special focus on the contribution of autoantibodies and cytokine-inducing properties of IC. In the autoimmune disease SLE, increased levels of IC-induced cytokines were associated with both increased classical complement activation and the occurrence of the autoantibodies anti-SSA and anti-SSB, both directed against RNA-associated antigens. In addition, complement activation and anti-SSA synergistically predisposed to higher levels of IC in sera. In the following study it was demonstrated that also other autoantibodies against RNA-associated autoantigens were more enriched than anti-dsDNA in SLE IC. Sudanese Visceral Leishmaniasis (VL) patients had elevated IC levels, and precipitated IC induced higher levels of GM-CSF, IL10, IL6 and IL1RA than control IC. Levels of IC were especially prominent in severely ill patients receiving antimony treatment, and a parallel association with IC induction of GM-CSF was demonstrated. Leishmania-infected patients were often rheumatoid factor (RF) positive and a substantial number displayed reactivity towards cyclic citrullinated peptide (CCP) antigens. Contrary to what was seen in Sudanese RA sera, the CCP reactivity was not restricted to citrulline but reacted equally well with arginine-containing control peptides. Levels of anti-CCP among VL patients were not due to cross-reactions with, or CCP-reactivity bound to IC. I have demonstrated that IC are associated with the presence of autoantibodies in both SLE and in Leishmania infection. In SLE, autoantibodies against RNA-associated antigens were more prone to form circulating IC than anti-dsDNA. In Leishmania infection false reactivity against the CCP-autoantigen correlated to IC levels although the IC themselves did not contain such reactivity. In both diseases higher IC levels were associated with a more active disease, and purified IC induced key cytokines in disease pathogeneses.

Multiple sclerosis (MS) is an autoimmune disorder of the central nervous system (CNS). In the current thesis, we have preformed an immunological investigation of patients with MS and developed an immunosuppressive cell therapy that could be beneficial for these patients. MS has been considered to be driven by T helper type1 (Th1) lymphocytes but new data indicate the involvement of Th17 responses. T cells from patients with MS that were evaluated for immunological status secreted both interferon-γ and interleukin-17 upon stimulation. However, T cells from patients with MS in remission, in contrast to relapse, had poor proliferative capacity suggesting that they are controlled and kept in anergy. T regulatory cells (Tregs) are important to maintain self-tolerance and the role of CD4+CD25+FoxP3+ Tregs in autoimmunity has been extensively investigated. We analyzed Tregs from patients with MS in relapse and remission by multicolor flow cytometry for the expression of CD3, CD4, IL2R (CD25), FoxP3 and the IL7R (CD127). Patients in relapse exhibited higher levels of FoxP3-positive Tregs lacking CD25 compared to healthy controls, indicating that Tregs might attempt to restrain immune activity during relapse. In the murine experimental autoimmune encephalomyelitis (EAE) model of MS, therapy with suppressive cells such as Tregs or mesenchymal stromal cells (MSCs) has proven beneficial. However, systemic administration of such cells may immunologically compromise the recipient and promote infections due to general immunosuppression. We hypothesized that suppressive cells can be equipped with a CNS-targeting receptor and be delivered intra-nasally to avoid systemic exposure. CD4+ T cells were modified with a lentiviral vector system to express a myelin oligodendrocyte (MOG)-targeting receptor in trans with the FoxP3 gene that drives Treg differentiation. Genetically engineered Tregs demonstrated suppressive capacity in vitro and localized to the brain and suppressed ongoing encephalomyelitis in vivo. Cured mice were rechallenged with an EAE-inducing inoculum but remained healthy. MSCs are a heterogeneous population of stromal cells residing in most connective tissues and have the capacity to suppress effector cells of the immune system. MSCs were engineered to express MOG-targeting receptors using lentiviral vectors. Genetically engineered MSCs retained their suppressive capacity in vitro and successfully targeted the brain upon intranasal delivery. Engineered MSCs cured mice from disease symptoms and these mice were resistant to further EAE challenge. Encephalitic T cells isolated from cured mice displayed an anergic profile while peripheral T cells were still responsive to stimuli. In conclusion, MS patients have peripheral CNS-reactive T cells of both Th1 and Th17 type that, while in remission, are kept in anergy. Also, MS patients in relapse exhibit increased levels of CD25 negative Tregs indicating an attempt to restrain immune activity. Finally, immunosuppressive cells can be genetically engineered to target CNS and efficiently suppress encephalomyelitis in an active EAE model upon intranasal delivery.

During pregnancy, the woman carries a fetus partly foreign to her immune system, because of the expression of paternal antigens. Despite this, the fetus is normally tolerated and not rejected, as is often the case with organs in allogeneic transplantations. Systemic changes in maternal blood occur during pregnancy but, perhaps of greater importance, are changes in tissues locally in the uterus. The pregnant uterine endometrium, the decidua, is infiltrated by large numbers of leukocytes, mainly natural killer (NK) cells but also macrophages and T lymphocytes. Further, various cytokines are known to be secreted at the fetomaternal interface. However, the functions of these cells and the cytokine networks are not fully understood. The aim of this thesis was to investigate the local immune balance in normal human pregnancy decidua, both in the early phase of pregnancy and at parturition. First trimester decidual mononuclear cells, NK cells and macrophages were all shown to secrete IFN-γ, IL-4 and IL-10, as detected by ELISPOT. The secretion was not mirrored in blood from the same subjects. A significantly larger number of decidual macrophages secreted IL-10 than did their blood counterparts, indicating potential regulatory functions of this cell type. Further examination of early pregnancy decidual macrophages by microarray revealed 120 genes being differentially regulated at the transcriptional level in decidual compared to blood monocytes/macrophages. Several genes were associated with alternative activation/M2 polarization of macrophages, including CCL-18, CD209, IGF-1, MRC-1 and FN-1. Genes connected to immune regulation and tissue remodelling were common, in line with the potential functions for this cell type in utero. In addition, some molecules not previously connected to decidual macrophages, such as TREM-2, A2M and PGDS, were found to be upregulated, gaining new insights into the regulatory functions of decidual macrophages. Term decidual mononuclear cells spontaneously secrete IFN-γ, TNF, IL-4, IL-10, and TGF-β. No differences were seen between tissues obtained before and after the onset of labour, indicating that decidual mononuclear cells are not the main cell population responsible for plausible cytokine regulation in the process of labour induction. Placental and fetal membranes as well as cells in the maternal systemic circulation may instead contribute to a possible shift in immune balance prior to pregnancy termination. In conclusion, decidual leukocytes, including NK cells and macrophages, are potential producers of both Th1-like/pro-inflammatory and Th2-like/anti-inflammatory cytokines in early pregnancy as well as at parturition. Decidual macrophages are of a specialized phenotype with effector functions contributing to a proper invasion of the placenta and to immunological protection of the semi-allogeneic fetus. This thesis adds new knowledge on local immune balance during normal human pregnancy, however, the clinical significance of the presented data needs to be clarified.

<p><em>Background </em>The proliferation signal inhibitors (PSIs) sirolimus (SRL) and everolimus (ERL) are the potent immunosuppressive drugs using in organ transplantation and has been used successfully in renal transplant recipients (RTX) as well. PSIs are the key factors to overcome the allograft rejections after successful organ transplantation since the immune system starts to react against the graft. SRL and ERL prevents the action of immune system b inhibits the proliferation of T- and B-cells by inhibiting the intracellular signaling of interleukin-2. The presence of excess amount of serum proteins including albumin in the urine is considered as proteinuria, which reflects the loss of kidney function. The occurrence of proteinuria can be the result of abnormal glomerular filtration and/or impaired tubular endocytic function of renal proximal tubular epithelial cells (PTECs). Megalin and cubulin are two scavenger receptors present on epical surface of PTECs and involved in reabsorption of proteins after glomerular ultrafiltration process in the kidney. Proteinuria appears too high in renal transplanted patients during ongoing   treatment with PSIs.</p><p><em>Aim</em> Our study aimed to investigate and correlate the expression level of megalin and cubilin and albumin uptake in PTEC of renal transplanted patients before and after conversion to PSI.</p><p><em>Methods</em> To retrieve the maximal expression of our interest molecules in renal PTECs, we optimized antigen retrieval (AR) method and primary antibody dilution for each molecule separately. An optimization experiment was performed on 3 different normal patients renal biopsies were used. Later, human renal biopsy specimens originated from 4 different renal transplanted patients were used in this study. From all the 4 patients biopsy specimens were taken before and ongoing administration of PSIs (SRL, ERL). The expression of megalin, cubilin and albumin uptake in PTEC of renal transplant patients was determined by immunohistochemical staining.</p><p><em>Results</em> Based on the optimization experiments, we selected the AR method and primary antibody dilution for the expression of megalin, cubilin and albumin uptake. In 4 renal transplanted patients following administration of PSIs results in patients 1, 2, 3 expression of megalin, cubilin and albumin uptake during ongoing PSI treatment was not comparable or even more intense than before PSIs introduction. The expression of megalin, cubilin and albumin uptake was reduced in patient 4 during ongoing PSI treatment.</p><p><em>Conclusion</em> Our findings suggest that the renal transplant patient 4 developed proteinuria during PSI medication. The expression of megalin, cubilin and albumin uptake was markedly decreased during ongoing PSI treatment in patient 4. We concluded that there is a direct link between PSI medication and tubular dysfunction, which might cause proteinuria</p>