摘要：Lupus nephritis (LN) is one of the most severe manifestations of Systemic lupus erythematosus (SLE). Presence of anti-C1q autoantibodies correlates with active LN and is associated with proliferative lupus nephritis, specifically class IV. These autoantibodies bind to neo-epitopes within the collagen region of C1q. Recently we found that anti-C1q autoantibodies from LN sera, recognized epitopes within the globular domain (gC1q) of C1q (anti-gC1q antibodies). We established that anti-gC1q antibodies against B-chain inhibited the interactions of C1q with IgG and CRP. The aim of present study was to investigate the relationship between serum anti-ghB C1q antibodies levels and some renal pathological characteristics in LN, as well as to evaluate whether these antibodies had a potential to be measured as a non-invasive marker for assessment of disease activity. Anti-C1q autoantibodies, complement proteins - C1q, C4 and C3, IgG- and IgM-containing circulating immune complexes (CICs) levels were screened by ELISA in 46 LN patients. Complement hemolytic activity was detected by CH50 test. The presence of ANA and anti-dsDNA antibodies were detected by double immunodiffusion assays and indirect immunofluorescence. Sera from 196 normal donors served as controls. 30.43% (n=14) of patients were seropositive for anti-C1q autoantibodies and seven of them were seropositive for anti-ghB C1q autoantibodies. Correlations between levels of C1q, C4, and C3 as markers for complement activity and anti-C1q or anti-ghB C1q autoantibodies were not significant. We found significant correlations between IgG CIC and anti-C1q antibodies (r = 0.586; p = 0.001) as well as between IgG CIC and anti-ghB C1q antibodies (r = 0.323; p = 0.048). Presence of anti-C1q or anti-ghB C1q antibodies significantly correlated with activity of LN as determined by SLEDAI (r = 0.425; p = 0.008 and r = 0.372; p = 0.048). The both anti-C1q and anti-ghB C1q antibodies significantly correlated with the severity of nephritis, which manifested as proteinuria g/24 h (r =0.454 p = 0.007 and r =0.371 p = 0.031) and low serum albumin (r=-0.377, p=0.031 and r=-0.401, p=0.021). Anti-C1q but not anti-ghB C1q antibodies correlated with anti-ds DNA antibodies (r = 0.482; p = 0.043). Anti-ghB C1q have properties to be useful marker in making predictions of renal histopathology in LN and assessment of disease activity
关键词：anti-C1q autoantibodies; Lupus nephritis; C1q; C1q B chain
