Anti-C1q autoantibodies from patients with systemic lupus erythematosus induce C1q production by macrophages

Antibodies against C1q (anti-C1q) are frequently found in patients with systemic lupus erythematosus (SLE). The anti-C1q antibodies strongly correlate with the occurrence of lupus nephritis and low-circulating C1q levels. Previous studies have demonstrated that myeloid cells, i.e., dendritic cells and macrophages, are a major source of C1q. However, a direct effect of anti-C1q on C1q secretion by macrophages has not yet been established. In the...