Study on Proteinase-lnhibiting Capacity of Plasma α ₂-Macroglobulin in Idiopathic Nephrotic Syndrome

Abstract

We studied the relationship between plasma α₂-macroglobulin (α₂M) and depressed cell-mediated immunity in idiopathic nephrotic syndrome (INS). Plasma α₂M concentrations (μmol/l) were increased during relapses of INS; however, the proteinase inhibitory activity, measured using bacterial thermo-lysin, was significantly decreased when calculated per 1 mol of α₂M, implying a reduced proteinase-inhibiting capacity of α₂M. The decreased proteinase-inhibiting capacity of α₂M was associated with the inhibitory activity of plasma on normal lymphocyte blastogenesis. Purified α₂M, when complexed with chymotrypsin, intensively inhibited normal lymphocyte blastogenesis induced by concanavalin A, as compared with the free form of α₂M. From these results it is suggested that, although the amount of α₂M protein has increased in the plasma of INS patients during relapse, its binding capacity to proteinases has relatively decreased. The results of this study may provide speculation for both the well-known high plasma α₂M concentrations and the immunodepres-sion, both of which have been observed in INS patients in the past few decades.