Use of complement receptor 1 (CD35) assay in the diagnosis and prognosis of immune complex mediated glomerulopathies

Complement Receptor 1 (CR1) is a polymorphic glycoprotein expressed on eryt hrocytes, leukocytes and glomerular podocytes and has a major role in immun e complex processing. In addition, it regulates the complement cascade acti vation by preventing formation of classical and alternative pathway convert ases and by acting as a cofactor for Factor I mediated cleavage of C3. In t his study, we have examined the expression of erythrocyte CR1 (E-CR1) and g lomerular CR1 (G-CR1) in different kinds of nephropathies using ELISA and i mmunofluorescence microscopy to understand their role in immune complex (IC ) mediated renal diseases. E-CR1 was significantly reduced in all categorie s of lupus nephritis in comparison to normal subjects and non-IC renal dise ases. However, other IC mediated diseases like IgA nephropathy and membrano proliferative glomerulonephritis had normal E-CR1 levels. G-CR1 showed dist inct differences between IC and non-IC mediated diseases. G-CR1 was virtual ly absent in lupus kidneys. In other IC mediated diseases, there was a corr elation of G-CR1 expression to the IC and complement fragment deposition. G -CR1 serves as a useful diagnostic marker for IC mediated diseases while E- CR1 is useful as a prognostic marker to monitor the course of disease after the treatment has initiated.