Multiple serum inhibitors of lectin-induced lymphocyte proliferation in nephrotic syndrome.

Inhibitory activity on PHA- and Con A-induced lymphocyte proliferation was observed in the serum of 29 patients with nephrotic syndrome (NS); this inhibitory activity was present both in steroid-sensitive nephrotic syndrome (SSNS; 18 patients) and in NS due to other glomerulopathies (11 patients). In order to characterize the inhibitory activity, peripheral blood lymphocytes from normal donors were stimulated with various concentrations of Con A in culture medium supplemented with: (1) 20% SSNS serum, (2) various concentrations (1, 5 and 20%) of either SSNS serum or normal human serum (NHS) and (3) 20% of a serum prepared by mixing different proportions of SSNS and NHS. The results suggest that the inhibitory activity is due to at least two different factors: (a) inhibitor(s) acting competitively with the lectin Con A, and (b) inhibitor(s) neutralized by factor(s) present in NHS. A disturbance in the normal equilibrium between inhibiting and enhancing factors which results in overall inhibition might well be a consequence of the marked alteration in serum proteins characteristic of NS.