Purpose: We tested the hypothesis that some abnormalities of immune functions are genetically controlled in patients with systemic lupus erythematosus (SLE).
Subjects and methods: We used a phytohemagglutinin-induced interleukin-2 (IL-2) activity assay and a spontaneous plaque-forming cell assay to evaluate T-cell and B-cell function, respectively, in 34 clinically healthy family members of six SLE probands.
Results: Impaired IL-2 activity was found in 15 of the 29 consanguineous relatives. There was no relation between the household relatives and the nonhousehold relatives; none of the five nonconsanguineous household persons had abnormal results. Results for the B-cell assay were abnormal in 22 of the 29 consanguineous relatives. The B-cell abnormalities were more commonly observed in the consanguineous household relatives; four of the five nonconsanguineous household relatives also had abnormal assay results.
Conclusion: The findings indicate that the impaired IL-2 activity in relatives appears to strongly correlate with a genetic relationship. Although the evidence favors a genetic basis for the B-cell abnormalities, environmental effects may also contribute to the familial occurrence of these abnormalities.