Objective: To determine if antibodies to the collagen-like region of C1q (C1q-CLR) are present in the glomerular immune deposits of patients with systemic lupus erythematosus (SLE).
Methods: Kidney tissues were obtained at autopsy, glomeruli were isolated, and glomerular basement membrane fragments were prepared. Antibodies were extracted with low pH or with DNase.
Results: The concentrations of antibodies to C1q-CLR recovered from the glomeruli were > or =50-fold higher per unit of IgG than that found in the serum or in the serum and interstitial fluid entrained in glomeruli. Antibodies to C1q-CLR were recovered from glomeruli of 4 of 5 patients with proliferative glomerulonephritis at autopsy.
Conclusion: This is the first demonstration that antibodies to C1q-CLR are deposited and concentrated in the renal glomeruli of patients with SLE. These antibodies, thus, have the potential of contributing to the pathogenesis of lupus glomerulonephritis.