Epidemiology of anti-lymphocyte antibodies in systemic lupus erythematosus.

Lymphocytotoxic antibodies (LCTA) occur in 80% of SLE patients and 40% to 60% of their asymptomatic relatives. They occur equally in consanguineous and nonconsanguineous relatives, are more common with close proband contact, and vary directly with LCTA activity in the proband. LCTA are also increased in laboratory personnel handling SLE blood. Anti-RNA antibodies are found in SLE patients and consanguineous relatives. Both antibodies are primarily IgM in relatives but are IgM and IgG in SLE patients.