Immunologic observations on 9 sets of twins either concordant or discordant for SLE.

The influence of genetic and nongenetic factors on abnormalities of the immune response in systemic lupus erythematosus (SLE) was studied in 9 sets of twins in which one or both twins had SLE. Particular emphasis was placed on contrasting the results between the sibs of 3 monozygotic pairs discordant for clinical SLE. Depression of cell-mediated immunity, determined by lymphocyte blastogenic response to mitogens, was associated with the clinical expression of illness. In contrast, autoreactive antilymphocyte antibodies and lymphocyte tubuloreticular structures were found in both clinically affected and unaffected subjects and were more prominently associated with the presence of other serologic abnormalities. No evidence of antigens or cell surfaces determinants unique to affected sibs was encountered.