Expression of complement regulatory proteins on erythrocytes from patients with idiopathic focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a heterogeneous group of disorders with respect to aetiology, morphology, clinical course and response to treatment. The present study assessed the expression of complement receptor 1 (CR1), decay accelerating factor (DAF) and membrane inhibitor of reactive lysis (CD59) on the erythrocytes of FSGS patients using flow cytometry compared with their expression on the erythrocytes of minimal change nephrotic syndrome (MCNS) patients. Significantly reduced expression of CR1, DAF and CD59 was observed on the erythrocytes of FSGS patients compared with the reduced expression of CR1 and enhanced expression of DAF on the erythrocytes of MCNS patients. A significant inverse relationship was demonstrated between CR1 expression and proteinuria levels in FSGS patients (r = 0.55, P < 0.01). A follow-up study of 12 patients with FSGS after immunosuppressive therapy showed that the levels of complement regulatory proteins are significantly increased when the disease goes into remission. However, in patients not responding to immunosuppressive therapy, levels of these proteins remained low. MCNS patients showed significant increases in CR1 and decreases in DAF expression during remission of the disease.