Immunosuppressive factors in uraemic sera are composed of both dialysable and non-dialysable components.

The immunosuppressive factors in uraemic sera were studied. Sera were obtained from 46 uraemic patients with a mean serum creatinine of 1.24 mM/1 +/- 0.36 (s.d.) prior to being introduced to dialysis therapy. Normal peripheral blood mononuclear cells, which were incubated in vitro with pokeweed mitogen (PWM) in the presence of 10% uraemic sera plus 10% pooled normal human serum sustaining the culture, showed decreased 3H-thymidine uptake compared to the control culture with normal sera. The immunosuppressive activity of uraemic sera was partially lost by in vitro dialysis, although a moderate degree of suppressive potency to the normal cells cultured with PWM remained in the dialysed uraemic sera. The remaining inhibitory activity in the dialysed sera was found to be unrelated to anti-lymphocyte antibodies.