Autoantibodies Against C3b—Functional Consequences and Disease Relevance

The complement component C3 is at the heart of the complement cascade. It is a complex protein, which generates different functional activated fragments (C3a, C3b, iC3b, C3c, C3d). C3b is a constituent of the alternative pathway C3 convertase (C3bBb), binds multiple regulators, and receptors, affecting thus the functioning of the immune system. The activated forms of C3 are a target for autoantibodies. This review focuses on the discovery, disease relevance, and functional consequences of the anti-C3b autoantibodies. They were discovered about 70 years ago and named immunoconglutinins. They were found after infections and considered convalescent factors. At the end of the twentieth century IgG against C3b were found in systemic lupus erythematosus and recently in lupus nephritis, correlating with the disease severity and flare. Cases of C3 glomerulopathy and immune complex glomerulonephritis were also reported. These antibodies recognize epitopes, shared between C3(H2O)/C3b/iC3b/C3c and have overt functional activity. They correlate with low plasmatic C3 levels in patients. In vitro, they increase the activity of the alternative pathway C3 convertase, without being C3 nephritic factors. They perturb the binding of the negative regulators Complement Receptor 1 and Factor H. The clear functional consequences and association with disease severity warrant further studies to establish the link between the anti-C3b autoantibodies and tissue injury. Comparative studies with such antibodies, found in patients with infections, may help to uncover their origin and epitopes specificity. Patients with complement overactivation due to presence of anti-C3b antibodies may benefit from therapeutic targeting of C3

Prevalence and Significance of Non-conventional Antiphospholipid Antibodies in Patients With Clinical APS Criteria

Background: The biological diagnostics of antiphospholipid syndrome (APS) takes into account the persistent positivity for anticardiolipin and/or anti-β2GP1 antibodies and/or presence of lupus anticoagulant (LA). However, some non-conventional antiphospholipid antibodies have emerged that could help in the diagnosis of APS.Objectives: To study the potential usefulness of non-conventional antiphospholipid antibodies in clinical practice.Methods: Eighty-seven patients, aged from 15 to 92 years were included and classified in following groups: 41 patients positive for the conventional antibodies with clinical criterion of APS (31 with primary APS and 10 secondary), 17 seronegative APS (SNAPS) patients (i.e., persistent negativity for the conventional antibodies with a strong clinical suspicion of APS), 11 asymptomatic antiphospholipid antibodies carriers (i.e., persistent positivity for the conventional antibodies without clinical evidence of APS), and 18 patients presenting with a first thrombotic or obstetrical event. IgG and IgM were detected to the following antigens: phosphatidylserine/prothrombin (PS/PT) by ELISA, and phosphatidic acid, phosphatidyl-ethanolamine, phosphatidyl-glycerol, phosphatidyl-inositol, phosphatidylserine, annexin V, prothrombin by immunodot. Anti-β2GP1 IgA, and anti-β2GP1 domain 1 IgG were detected by chemiluminescence.Results: Positivity for the non-conventional antibodies was correlated with APS severity; patients with catastrophic APS (CAPS) being positive for 10.7 (Median, Range: 5–14) non-conventional antibodies. 9/17 seronegative patients were positive for at least one of non-conventional antibodies. A study of non-supervised hierarchical clustering of all markers revealed that anti-PS/PT antibodies showed high correlation with the presence of LA. All patients with APS triple positivity (highest risk profile) exhibited also persistent positivity for anti-PS/PT antibodies.Conclusions: Our data obtained from a prospective cohort constituted mainly by patients with primary APS, suggest that non-conventional APS antibodies may be useful for patients classified as SNAPS. They demonstrate the potential value of aPS/PT antibodies as a strong marker of APS. We propose that anti-PS/PT antibodies could be a surrogate APS biological marker of LA to classify in high-risk profile patients treated by direct oral anticoagulants (DOACs), in whom LA detection cannot be achieved

Mutations in components of complement influence the outcome of Factor I-associated atypical hemolytic uremic syndrome

Genetic studies have shown that mutations of complement inhibitors such as membrane cofactor protein, Factors H, I, or B and C3 predispose patients to atypical hemolytic uremic syndrome (aHUS). Factor I is a circulating serine protease that inhibits complement by degrading C3b and up to now only a few mutations in the CFI gene have been characterized. In a large cohort of 202 patients with aHUS, we identified 23 patients carrying exonic mutations in CFI. Their overall clinical outcome was unfavorable, as half died or developed end-stage renal disease after their first syndrome episode. Eight patients with CFI mutations carried at least one additional known genetic risk factor for aHUS, such as a mutation in MCP, CFH, C3 or CFB; a compound heterozygous second mutation in CFI; or mutations in both the MCP and CFH genes. Five patients exhibited homozygous deletion of the Factor H-related protein 1 (CFHR-1) gene. Ten patients with aHUS had one mutation in their CFI gene (Factor I-aHUS), resulting in a quantitative or functional Factor I deficiency. Patients with a complete deletion of the CFHR-1 gene had a significantly higher risk of a bad prognosis compared with those with one Factor I mutation as their unique vulnerability feature. Our results emphasize the necessity of genetic screening for all susceptibility factors in patients with aHUS

Natural killer cells in the human lung tumor microenvironment display immune inhibitory functions

Background Natural killer (NK) cells play a crucial role in tumor immunosurveillance through their cytotoxic effector functions and their capacity to interact with other immune cells to build a coordinated antitumor immune response. Emerging data reveal NK cell dysfunction within the tumor microenvironment (TME) through checkpoint inhibitory molecules associated with a regulatory phenotype.Objective We aimed at analyzing the gene expression profile of intratumoral NK cells compared with non-tumorous NK cells, and to characterize their inhibitory function in the TME.Methods NK cells were sorted from human lung tumor tissue and compared with non- tumoral distant lungs.Results In the current study, we identify a unique gene signature of NK cell dysfunction in human non-small cell lung carcinoma (NSCLC). First, transcriptomic analysis reveals significant changes related to migratory pattern with a downregulation of sphingosine-1-phosphate receptor 1 (S1PR1) and CX3C chemokine receptor 1 (CX3CR1) and overexpression of C-X-C chemokine receptor type 5 (CXCR5) and C-X-C chemokine receptor type 6 (CXCR6). Second, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and killer cell lectin like receptor (KLRC1) inhibitory molecules were increased in intratumoral NK cells, and CTLA-4 blockade could partially restore MHC class II level on dendritic cell (DC) that was impaired during the DCs/NK cell cross talk. Finally, NK cell density impacts the positive prognostic value of CD8+ T cells in NSCLC.Conclusions These findings demonstrate novel molecular cues associated with NK cell inhibitory functions in NSCLC

Atypical Hemolytic Uremic Syndrome Associated With Complement Factor H Autoantibodies and CFHR1/CFHR3 Deficiency

Although genetic defect of complement factor H (CFH) is a common cause of atypical hemolytic uremic syndrome (aHUS), development of autoantibodies to CFH (CFH-Ab) is also known to be an acquired cause of aHUS. Recently, a correlation between the development of CFH-Ab and the deficiency of the CFH-related proteins, CFHR1 and CFHR3, was identified. In this study, plasma complement profiles were measured and genetic analysis of the CFH, CFI, MCP, CFHR1, and CFHR3 genes were performed in three female patients diagnosed with aHUS with positive CFH-Ab. Acute stage plasmas of all the three patients revealed low C3, low or low-normal CFH antigenic levels, and high titers of CFH-Ab. All the patients also showed complete plasma CFHR1 deficiency and homozygous genomic deletion of CFHR1/CFHR3, but none had CFH, CFI, or MCP mutations. All the patients were treated with plasmapheresis, and two patients required additional immunosuppressive therapy. These patients had a novel subgroup of aHUS characterized by a combination of genetic (a homozygous deletion of CFHR1/CFHR3) and acquired (development of CFH-Ab) factors. Patients with this disease may need intensive immunosuppressive therapy in addition to plasmapheresis. Screening for CFH-Ab and the CFHR1/CFHR3 deficiency should be included in the diagnostic tests for patients with aHUS.Supported by a Grant A080588 from the Korea Healthcare technology R&D Project, Ministry for Health, Welfare and Family Affairs, Republic of Korea and a Grant 06-2008-192-9 from the Seoul National University Hospital.LEQUINTREC M, 2009, AM J TRANSPLANT, V9, P1223Fremeaux-Bacchi V, 2008, BLOOD, V112, P4948, DOI 10.1182/blood-2008-01-133702Kwon T, 2008, NEPHROL DIAL TRANSPL, V23, P2088, DOI 10.1093/ndt/gfn063Jozsi M, 2008, BLOOD, V111, P1512, DOI 10.1182/blood-2007-09-109876Kavanagh D, 2008, ANNU REV MED, V59, P293, DOI 10.1146/annurev.med.59.060106.185110Jozsi M, 2007, BLOOD, V110, P1516, DOI 10.1182/blood-2007-02-071472Sellier-Leclerc AL, 2007, J AM SOC NEPHROL, V18, P2392Zipfel PF, 2007, PLOS GENET, V3, P387, DOI 10.1371/journal.pgen.0030041de Jorge EG, 2007, P NATL ACAD SCI USA, V104, P240, DOI 10.1073/pnas.0603420103Venables JP, 2006, PLOS MED, V3, P1957, DOI 10.1371/journal.pmed.0030431Caprioli J, 2006, BLOOD, V108, P1267, DOI 10.1182/blood-2005-10-007252Vaziri-Sani F, 2006, KIDNEY INT, V69, P981, DOI 10.1038/sj.ki.5000155HEINEN S, 2006, HUM MUTAT, V27, P292Jozsi M, 2006, J AM SOC NEPHROL, V17, P170, DOI 10.1681/ASN.2005080868Kavanagh D, 2006, BRIT MED BULL, V77-78, P5, DOI 10.1093/bmb/ldl004Lupski JR, 2005, PLOS GENET, V1, P627, DOI 10.1371/journal.pgen.0010049Fremeaux-Bacchi V, 2005, J MED GENET, V42, P852, DOI 10.1136/jmg.2005.030783Dragon-Durey MA, 2005, SPRINGER SEMIN IMMUN, V27, P359, DOI 10.1007/s00281-005-0003-2Jokiranta TS, 2005, AM J PATHOL, V167, P1173Noris M, 2005, J AM SOC NEPHROL, V16, P1035Esparza-Gordillo J, 2005, HUM MOL GENET, V14, P703, DOI 10.1093/hmg/ddi066Dragon-Durey MA, 2005, J AM SOC NEPHROL, V16, P555Atkinson JP, 2005, ANN NY ACAD SCI, V1056, P144, DOI 10.1196/annals.1352.032Coppo P, 2004, MEDICINE, V83, P233, DOI 10.1097/01.md.0000133622.03370.07Dragon-Durey MA, 2004, J AM SOC NEPHROL, V15, P787Neumann HPH, 2003, J MED GENET, V40, P676Manuelian T, 2003, J CLIN INVEST, V111, P1181, DOI 10.1172/JCI200316651Hellwage J, 2002, J IMMUNOL, V169, P6935Male DA, 2000, MOL IMMUNOL, V37, P41Zipfel PF, 1999, IMMUNOPHARMACOLOGY, V42, P53KRISTENSEN T, 1986, P NATL ACAD SCI USA, V83, P3963SCHWARTZ GJ, 1976, PEDIATRICS, V58, P2591

Natural killer cells in the human lung tumor microenvironment display immune inhibitory functions

Background Natural killer (NK) cells play a crucial role in tumor immunosurveillance through their cytotoxic effector functions and their capacity to interact with other immune cells to build a coordinated antitumor immune response. Emerging data reveal NK cell dysfunction within the tumor microenvironment (TME) through checkpoint inhibitory molecules associated with a regulatory phenotype. Objective We aimed at analyzing the gene expression profile of intratumoral NK cells compared with non-tumorous NK cells, and to characterize their inhibitory function in the TME. Methods NK cells were sorted from human lung tumor tissue and compared with non- tumoral distant lungs. Results In the current study, we identify a unique gene signature of NK cell dysfunction in human non-small cell lung carcinoma (NSCLC). First, transcriptomic analysis reveals significant changes related to migratory pattern with a downregulation of sphingosine-1-phosphate receptor 1 (S1PR1) and CX3C chemokine receptor 1 (CX3CR1) and overexpression of C-X-C chemokine receptor type 5 (CXCR5) and C-X-C chemokine receptor type 6 (CXCR6). Second, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and killer cell lectin like receptor (KLRC1) inhibitory molecules were increased in intratumoral NK cells, and CTLA-4 blockade could partially restore MHC class II level on dendritic cell (DC) that was impaired during the DCs/NK cell cross talk. Finally, NK cell density impacts the positive prognostic value of CD8 + T cells in NSCLC. Conclusions These findings demonstrate novel molecular cues associated with NK cell inhibitory functions in NSCLC