Erythropoietin therapy in humans increases erythrocyte expression of complement receptor type 1 (CD35)

The expression of complement receptor Type 1 (CR1, CD35) on erythrocytes (E) is unique to humans and other primates. E-CR1, a C3b/C4b receptor that also acts as cofactor for Factor I, appears to be important in clearing C3/C4-opsonized immune complexes from the circulation, in controlling complement activation in the circulation, and in regulating antibody formation. This study was undertaken to determine whether therapy with recombinant human erythropoietin (rEPO) might increase E-CR1 expression in humans. The rationale is that young erythrocytes express more E-CR1 than old erythrocytes. Thus, conditions that stimulate erythropoiesis should increase E-CR1 expression. The hypothesis that stimulating erythropoiesis by rEPO therapy can increase E-CR1 expression was tested in six anemic chronic hemodialysis (ESRD) patients and five systemic lupus erythematosus (SLE) patients without renal failure. Before the rEPO therapy, three of the SLE patients were anemic and two were not. The ESRD patients were studied before and during 9 or 10 mo of rEPO therapy. The SLE patients were studied before, during, and after 7 mo of rEPO given by sc injection two or three times weekly. It was found that rEPO therapy was associated with a progressive increase in the average number of CR1/E in each of the ESRD patients and in the anemic SLE patients: mean baseline CR1/E was 210 +/- 50 (SE) for the ESRD patients and 125 +/- 35 for the SLE patients.(ABSTRACT TRUNCATED AT 250 WORDS)