The frequency of complement receptor type 1 (CR1) gene polymorphisms in nine families with multiple cases of systemic lupus erythematosus.

Low levels of complement receptor type 1 (CR1) on the erythrocytes of patients with systemic lupus erythematosus (SLE) may be acquired or genetically determined. Nine families with multiple cases of SLE were studied using a CR1 probe and restriction fragment length polymorphism analysis, to address this question. The absence of a significant increase in the frequency of a 6.9-kb band (previously shown to be associated with low-level CR1 on erythrocytes) suggests that this genetic marker does not play a major role in determining SLE, either in these families or in SLE patients in general.