SLE is a disease characterized by overproduction of various types of autoantibodies. Under certain circumstances, it is possible to detect the presence of autoantibodies directed against neoepitopes of complement system, as well. Neoepitopes are not present in native proteins, but develop with their structural alterations. The following antibodies come under known anticomplement auoantibodies: C3 nephritic factor, antibody directed against C1 inhibitor or antibodies directed against C1R (C1 receptor). Anti-C1q antibodies are concededly the most significant autoantibodies directed against complement system. They are present in about one third of patients with SLE and there is a correlation with clinical activity and the presence of lupus glomerulonephritis. High titers of anti-C1q antibodies are accompanied by decreased levels of C1, as well as C3 and especially C4 complement component. The presence of anti-C1q antibodies is not limited or specific for lupus only. They were described for the first time in case of HUVS (Hypocomplementemic Urticarial Vasculitis Sydrome), later in Felty’s syndrome, rheumatoid vasculitis, hepatitis C and in senescent population, as well. The association of anti-C1q antibodies, complement consumption and presence of renal affection in case of SLE calls into question, whether and how do these autoantibodies participate in organ affection pathogenesis. As shown in animal models of disease, the presence of both anti-dsDNA and anti-C1q antibodies is necessary for the genesis of lupus nephritis. Their mutual interaction triggers the mechanisms of development of renal affection mediated by immune complexes.

        Key words: systemic lupus erythematosus, complement system, anti-C1q antibodies