Anti C1q antibodies in cutaneous lupus erythematosus

Autoantibodies against C1q are strongly linked to immune-complex disorders like systemic lupus erythematosus (SLE). Although anti-C1q antibodies have received much interest in the recent years, their biological functions remain unclear. Anti-C1q antibodies are strongly associated with lupus nephritis. Recent studies describe apoptosis as a key player in LE pathogenesis and C1q is an important opsonin, playing a central role in the uptake of apoptotic blebs. The aim of this study was to evaluate serum anti C1q antibodies, C1q with circulating immune complexes and correlation between serology and cutaneous apoptosis in patients with cutaneous lupus erythematosus.

79 subjects were recruited and divided into 4 groups-13 healthy controls, 26 with discoid chronic lupus (DLE), 23 with systemic lupus erythematosus (SLE) and 17 with subacute lupus erythematosus (SCLE). Blood samples and skin punched-biopsy specimens were performed. Serum anti-C1q antibodies and C1q associated to the immune complexes concentrations were determined by ELISA. Cutaneous caspase-3 expression was evaluated by immunohistochemistry.

SLE and SCLE patients had significantly higher levels of anti-C1q antibodies and serum C1q-CIC levels when compared to healthy controls (p < 0.05). Serum anti-C1q antibodies correlated with proteinuria in SLE patients (p < 0.05). Anti C1q antibodies levels also correlated with cutaneous caspase 3 expression in SLE and SCLE patients (both p < 0.05).

Anti C1q antibodies might play a pathogenic role in SCLE pathogenesis and being positively associated with cutaneous apoptosis markers might be associated with a negative prognosis and secondary SLE development.