The expression of C3b receptors in the differentiation of discoid lupus erythematosus and systemic lupus erythematosus.

We studied the expression of the C3b receptor, CR1, on erythrocytes (E-CR1) of patients who, in spite of having mild systemic symptoms, were diagnosed as having discoid lupus erythematosus and followed accordingly. We found that E-CR1 was markedly reduced in these patients, similar to that seen in patients with systemic disease. In contrast, those patients with completely asymptomatic discoid lupus erythematosus had the same expression of E-CR1 as the normal population.