The complement system is one of the most ancient immune defense mechanisms, providing rapid protection against invading micro-organisms. It is essential for the complement cascade to be under tight regulation in order to prevent excessive production of complement proteins. C5a is the most potent anaphylotoxin produced by the complement system, it binds C5a receptor (C5aR, CD88) and C5L2 (GPR77). C5a binding to C5aR induces leukocyte chemotaxis and release of inflammatory mediators. Over-production of C5a is known to be involved in many inflammatory and pathological conditions such as RA, I1R injury and sepsis, making it an attractive therapeutic target. Human and mouse C5aR share low homology and blocking C5a/C5aR signaling with small molecules has been challenging. We generated human C5aR knockout/knockin (hC5aR KI) mice in which the mouse C5aR coding region was replaced with that of human C5aR to utilize them for the development of human therapeutics targeting C5aR. hC5aR KI mice showed normal development, and leukocytes from hC5aR KI mice responded well to mouse C5a. We used two approaches to generate monoclonal antibodies (mAbs) against hC5aR. We used a mouse cell line transfected with hC5aR or neutrophils from hC5aR KI mice to immunize wild-type mice and generated high-affinity antagonistic mAbs which are specific to human C5aR. Anti-hC5aR mAb 7F3 blocked C5a-induced signaling completely without agonistic activity in vitro. In the animal model of K/BxN inflammatory arthritis, 7F3 both prevented and reversed inflammation. Currently, the function of the second C5a receptor, C5L2, remains controversial. There are contradicting reports from C5L2 KO mice that were generated by independent groups. We assessed the function of human C5L2 using an antagonistic mAb that specifically blocks C5L2 function and not C5aR. In vitro analysis using the C5L2-blocking mAb showed that C5a does not signal via C5L2 to affect chemotaxis or phagocytosis by neutrophils, indicating that C5L2 is not a signaling receptor for C5a, at least in these cellular functions.

Diss. (sammanfattning) Uppsala : Univ., 2003. / Härtill 4 uppsatser.

Orientadores: Renata de Oliveira Mattos Graner, Flávia Sammartino Mariano Rodrigues / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-26T11:30:42Z (GMT). No. of bitstreams: 1 Oliveira_ThaisRossinide_M.pdf: 1438459 bytes, checksum: a127a667898930e41649ac3faebb8d1a (MD5) Previous issue date: 2014 / Resumo: Streptococcus sanguinis é uma espécie pioneira comensal das superfícies dos dentes, que também está envolvida na endocardite infecciosa. Sua alta prevalência na cavidade oral indica capacidade de adaptar-se e sobreviver a diversos fatores de defesa presentes nesse nicho. Para se adaptar ao ambiente e a fatores do hospedeiro, as bactérias utilizam-se de sistemas reguladores de transcrição de dois componentes (SDC), que modulam a regulação de genes em respostas a diferentes estímulos. Neste estudo avaliou-se o papel do SDC VicRK e CovR, na susceptibilidade de S. sanguinis a opsonização pelo sistema complemento. Para isso, foram analisados os níveis de deposição de C3b / iC3b na presença de soro em um total de sete cepas clínicas de S. sanguinis, e as frequências de fagocitose por polimorfonucleares (PMNs) do sangue humano foram comparados entre as cepas S. sanguinis SK36 e mutantes knockout de vicK (SKvic) e covR (SKcov), genes estes que codificam componentes VicK e CovR, respectivamente. A cepa de S. mutans U159 foi utilizada como referência. Resumidamente, as cepas foram incubadas com soro humano a 2 ou 20% por 30 min (37 ° C, 10% de CO2), lavadas, e a presença de C3b associada à superfície foi detectado utilizando anticorpos anti-C3b humano (conjugado com FITC), sendo quantificadas por citometria de fluxo. Para avaliar as frequências de fagocitose por PMNs, as cepas foram incubadas com sangue humano durante tempos de 5, 15, 30 e 60 min (37 ° C, 10% de CO2), fixadas e coradas com Giemsa. PMNs com bactérias intracelulares, foram contados utilizando um microscópio de luz (1000 x) e os resultados expressos em relação a análise de um total de 200 PMNs. Resultados: As percentagens de deposição de C3b em SKvic, SKcov e SK36 foram de 11,3 (± 2,61), 40,2 (± 1,46) e 37,9% (± 3,97), respectivamente. Percentagem de superfície C3b foi significativamente menor em cepas de S. sanguinis em comparação a cepa de S.mutans (Kruskal Wallis, p <0,05), e em SKvic em comparação a cepa SK36 (Kruskal Wallis, p <0,05). As frequências médias de fagocitose por PMNs não foram afetadas, e foram 88, 99,3 e 99% em SKvic, SKcov e SK36, respectivamente. Conclusão: a inativação do VicK, mas não de CovR, reduz a deposição de C3b em S. sanguinis SK36. Cepas de S. sanguinis também são menos suscetíveis a deposição de C3b em comparação a S. mutans / Abstract: Streptococcus sanguinis is a commensal pioneer species of the tooth surfaces, which is also involved in infectious endocarditis. Its high prevalence in the oral cavity indicates ability to survive to several host defense factors present in the oral niches. To sense and respond to environmental and host factors, bacteria apply regulatory two-component systems (TCSs), which modulate gene transcription in response to different stimuli. This study evaluated the role of TCS VicRK and CovR in S. sanguinis susceptibility to opsonization by the complement system. To this aim, a total of seven S. sanguinis strains were analyzed, and levels of deposition of C3b/iC3b on the present of serum, and the frequencies of phagocytosis by polymorphonuclear (PMNs) in human blood were compared between parent S. sanguinis strain SK36 and knockout mutants of vicK (SKvic) and covR (SKcov) (genes encoding VicK and CovR components, respectively). S. mutans strain U159 was used as reference. Briefly, strains were incubated with 2 or 20% of human serum during 30 min (37°C, 10%CO2), washed, and the presence of surface-associated C3b was detected using anti-human C3b antibodies (FITC conjugated), which were quantified by flow cytometry. To assess the frequencies of phagocytosis by PMN, strains were incubated with human blood during 5, 15, 30 and 60 min (37°C, 10% CO2), fixed and stained with Giemsa. PMN with intracellular bacteria were counted using a light microscope (1000 x) and expressed in relation to a total of 200 PMN analyzed. Results: The percentages of C3b deposition on SKvic, SKcov and SK36 were 11.3 (± 2.61), 40.2 (± 1.46) and 37.9% (± 3.97), respectively. Percentage of surface C3b was significantly lower in S. sanguinis strains compared to S. mutans (Kruskal Wallis, p < 0.05), and in SKvic compared to SK36 (Kruskal Wallis, p < 0.05). The mean frequencies of phagocytosis by PMN was not affected, and were 88, 99.3 and 99% in SKvic, SKcov and SK36, respectively. Conclusion: the inactivation of the vicK, but not of covR, reduces the deposition of C3b in S. sanguinis SK36. S. sanguinis strains are also less susceptible to C3b deposition compared to S. mutans / Mestrado / Microbiologia e Imunologia / Mestra em Biologia Buco-Dental

Thesis (doctoral)--University of Göteborg, 1997. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--University of Göteborg, 1997. / Added t.p. with thesis statement inserted.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Complement is activated via two pathways: classical (CCP) and alternative (ACP). The CCP has been demonstrated in the nurse shark. The ACP has not been demonstrated in any cartilagenous fish. Nurse shark serum was evaluated for complement activity by its ability to lyse heterologous erythrocytes. As CCP activity requires calcium and magnesium, activity of shark serum chelated with EGTA (a selective calcium chelator) or EDTA (a chelator of calcium and magnesium) was assessed. Activity remained in serum chelated with EGTA but not EDTA. Furthermore, activity of chelated serum was enhanced by added magnesium. Activation of shark complement by activators of mammalian ACP (zymosan, LPS, inulin, CVF) was assessed. Complement was activated by zymosan and LPS. Immunoblots were employed, with limited success, to demonstrate complement proteins in nurse shark serum. This study unequivocally demonstrates that the ACP is present in the primitive nurse shark.

<p>Both Multiple Sclerosis (MS) and Guillan-Barré syndrome (GBS) are neurological inflammatory demyelinating autoimmune diseases, with a probable antibody contribution. Complement proteins in both MS and GBS does play a role in inflammation and demyelination at pathogenesis, according to earlier scientific evidence. The aim of this examination project work was to investigate systemic and intrathecal complement activation in MS and GBS, to gain further knowledge that might be useful for development of future therapeutics targeting immune responses during those diseases. An additional aim was to develop a new ELISA method for detection of complement iC3.</p><p>By using sandwich ELISA, complement proteins C1q, C4, C3, fH and C3a were measured in plasma and cerebrospinal fluid (CSF) from persons within 4 different diagnostic groups; MS, other neurological diseases (OND), GBS and controls (C). An ELISA method to detect iC3 (hydrolysed C3) was also developed, including usage of SDS-PAGE. Results based on raw data and statistical analysis show significantly elevated levels of C3a (C3a/C3) in MS and decreased C3 in plasma. In CSF low levels of C4 and C3a/C3 in MS were detected, though correlation of C3a and C1q was positive. GBS reveal high levels of all complement proteins analysed in CSF except for C3, and a positive correlation of C3a and C1q as well as C3a and fH was found.</p><p>These results indicate that MS patients have systemic complement activation; however the activation pathway is not determined. Complement activation in MS may also occur intrathecally, with correlation analysis indicating a possible activation via the classical pathway. MS patients suffering from a more acute relapsing-remitting (RR) MS have a more prominent systemic complement activation compared to MS patients responding to beta-interferon treatment. Systemic increased C3a/C3 ratio may be a possible biomarker to distinguish more acute RR MS in an earlier step of MS pathogenesis and should be further investigated. GBS patients have an intrathecal complement activation that seems to occur via the classical pathway.</p>

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by production of a wide range of autoantibodies, multiple organ involvement and by local formation or tissue deposition of immune complexes (ICs) in the inflamed organs. In contrast to most systemic inflammatory conditions, and despite raised levels of pro-inflammatory cytokines, SLE flares are rarely reflected by elevated C-reactive protein (CRP), an important acute-phase reactant in man with homologs in vertebrates and several invertebrates. As a part of the innate immune system, CRP binds certain molecules exposed on the surface of dying cells/apoptotic bodies and on the surface of pathogens and mediates their elimination by uptake in the reticuloendothelial system. CRP also interacts with IgG-containing immune complexes, binds Fc receptors and activates the complement system via C1q. The aims of this thesis were to investigate the complement activation properties of CRP; to elucidate if anti-CRP antibodies occur in SLE and, if so, whether anti-CRP antibody levels correlate with disease activity in SLE; to test the hypothesis that autoantibodies to pro-inflammatory cytokines prevent rise of CRP; and to survey if autoantibodies to certain nuclear antigens or to CRP correlate with cytokine-inducing properties of ICs from SLE sera. We have demonstrated that CRP bound to phosphorylcholine is a powerful activator of the classical complement pathway already in the CRP concentration range 4 to 10 mg/L, but with a marked inhibition at CRP levels above 150 mg/L. Autoantibodies to the monomeric form of CRP were found in approximately 40 percent of SLE patients and in a few sera from patients with primary Sjögren’s syndrome, but not in rheumatoid arthritis or in inflammatory bowel disease. The anti-CRP antibody levels showed significant correlations to several laboratory and clinical measurements, and anti-CRP positivity was associated with renal involvement in SLE. Native CRP levels were not correlated with anti-CRP or anti-cytokine antibody levels. Hence, the presence of antibodies to monomeric CRP or to CRP-inducing cytokines is an unlikely explanation to the relative failure of CRP response in patients with active lupus. However, antibodies to TNFα were found in subnormal levels at disease flares, whereas antibodies to TGFβ were found in supranormal levels as compared to healthy subjects. In contrast to antibodies against CRP and DNA, anti-SSA and anti-SSB antibodies may regulate the inflammatory process in SLE by enhancing IC formation and subsequent production of cytokines such as IL-6, IL-10 and IL-12p40. Hypothetically, anti-CRP autoantibodies may be of pathogenic importance, for instance by binding to monomeric CRP on cell and tissue surfaces and thereby increasing the risk of extrahepatic deposition of apoptotic material and in situ formation of ICs. / On the day of the defence data the status of article I was Submitted and the tile was "C-reactive protein activates or inhibits the classical complement pathway in a concentration dependent manner" and the status of article V was: Submitted.

[Truncated abstract] For the convenience of the reader, detailed figures and tables have been enlarged and compiled in Appendix 2, at the end of this thesis. This thesis is presented as an approach to identify, annotate and detect genomic duplication and polymorphism within large genomic regions. To demonstrate this, I have used as a model, the genomic region known as the Regulators of Complement Activation (RCA). The RCA complex is located on the long arm of chromosome 1 at position 1q32 and is a reservoir of complement regulatory proteins. The genes of the RCA share many similarities implying that all have arisen through multiple complex duplication events. My analysis of this region in the following chapters demonstrates the complexity of this duplication and identifies the many functional units within the RCA. It was my aim at the beginning of these studies to demonstrate an approach that could define the Ancestral Haplotypes (AHs) of the RCA gene cluster. To do this, extensive genomic analysis was required and the ever-increasing availability of genomic sequence has made this thesis possible. Each of the chapters serves to address the following aims set out at the beginning of this thesis: 1. Further characterise the relationship between the genes (Complement Control proteins-CCPs) and domains of the Regulators of Complement Activation (RCA). 2. Identify and examine the duplicated elements within the RCA. - 6 - 3. Examine the effects of retroviruses and other insertions and deletions (indels) in generating the divergence of duplicated genes. 4. Investigate the applicability of the Genomic Matching Technique (GMT) to define AH within the region. 5. Examine association of AHs with CCP implicated diseases. 6. Determine the GMT applicability in non-human species