Anti-nucleic acid antibodies in systemic lupus erythematosus patients and their families. Incidence and correlation with lymphocytotoxic antibodies.

Anti-RNA antibodies were found in 82% of 28 systemic lupus erythematosus (SLE) probands and in 16% of 124 of their family members. The incidence in 76 control family members was only 5%. In the SLE family members, the antibodies were found exclusively in 21% of the 94 close household contacts of the probands. The incidence of anti-native DNA (nDNA) antibodies was 68% for the SLE probands. The incidence of anti-nDNA antibodies in close household contacts of the probands was 6%, which was not significantly different from the 1% incidence found in control families. Lymphocytotoxic antibodies occurred in 57% of the SLE family members as a whole and in 68% of the close household contacts. In the SLE probands, lymphocytotoxic antibodies correlated with anti-single-stranded RNA (poly A) and anti-nDNA but not with anti-double-stranded RNA (poly A-poly U). On the other hand, lymphocytotoxic antibodies in the household contacts correlated with anti-double-stranded RNA (poly A-poly U) but not with anti-poly A or anti-nDNA. The anti-RNA antibodies were present in consanguineous household contacts but not in nonconsanguineous household contacts. These findings strengthen the hypothesis that both an environmental agent, possibly a virus, as well as the genetic response are important in the pathogenesis of SLE. Family members may therefore be a logical population in whom to search for specific antibodies to a viral agent.