Polynucleotide immune complexes in serum and glomeruli of patients with systemic lupus erythematosus

Abstract

Several types of antipolynucleotide antibodies were eluted by acid buffer or deoxyribonuclease treatment of glomeruli obtained from nine kidneys from patients with systemic lupus erythematosus (SLE). Anti-SDNA antibodies were found concentrated over serum levels in eight eluates, anti-NDNA in six eluates and anti-RNA Pr in four eluates; anti-DSRNA antibodies were not demonstrable in any eluate tested. Deoxyribonuclease treatment eluted a high incidence and greater quantity of anti-NDNA and anti-SDNA antibody, whereas anti-RNA Pr antibody was mainly eluted by acid buffer. Simultaneous studies of antibody and antigen in serial serum specimens and in glomeruli suggested that complexes of SDNA antibody or antigen excess were frequently deposited in SLE kidneys, in addition to complexes containing anti-NDNA and anti-RNA Pr. It was observed that studies of antibody titers alone were inadequate for predicting the types of complexes deposited in the kidney. Either antigen excess could obscure detection of humoral antibody or extremely high titers of antibody as observed for RNA Pr are not conducive to the formation of kidney localizing immune complexes in the absence of antigen. Immunofluorescence studies demonstrated the presence of SDNA antigen in most cases from which anti-SDNA antibody was eluted providing direct evidence for the presence of SDNA-anti-SDNA complexes in renal glomeruli. A study of complement components indicated that Clq was absent from cases in which little or no SDNA was deposited in renal glomeruli; although all nephritic kidneys demonstrated C3 deposits. Several hypotheses accounting for this observation are discussed, including the probable utilization of the alternate pathway by certain types of complexes and a direct reaction between C1q and circulating or tissue-bound NDNA or SDNA.