Serum complement activation of SLE patients during plasmapheresis

The erythrocyte complement receptor 1 (ECR1)-immune complex binding assay is a sensitive method for the determination of complement fragments which can be activated by bovine serum albumin (BSA)-anti-BSA in vitro. When the C3b/C4b containing bovine serum albumin (BSA)-anti-BSA was formed in the presence of the serum of patients with systemic lupus erythematosus (SLE) its binding to ECR1 was found to he lower than that formed in sera of normal volunteers, The plasmapheresis of SLE patients homozygous for the CR1/E high density allele displays a beneficial effect on the formation of C3b/C4b containing BSA-anti-BSA and its binding to ECR1, There was no significant correlation between the serum C3/C4 level and the percentage of C3b/C4b containing BSA-anti-BSA binding to the ECR1 of SLE patients during plasmapheresis, At the same time, there was an inverse correlation between the serum immune complex level and the ECR1 binding, which was significant in 3 of 5 cases, These data suggest that, besides the determination of different components of complement activation, the functional assay of complement activation might be useful in monitoring the effect of plasmapheresis in SLE.