Effects of urethan on lymphokine-producing activity of lymphocytes and on some functions of peritoneal macrophages in rats.

Effects of urethan on some functions of blood lymphocytes and peritoneal macrophages (PMs) of rats were studied in in vivo and in vitro experiments. The in vitro lymphokine (LK) producing activity of lymphocytes in the presence of specific antigen was depressed by urethan administered 1-5 days before the BCG sensitization. However, the drug injected after the BCG sensitization was not effective on the LK production. Urethan added to the cultures of previously BCG-primed lymphocytes did not influence the LK production. The sensitivity of glycogen-provoked PMs (pPM) to LK-induced activation and, at the same time, the 125I-IgG2a binding capacity as well as the EA rosette formation of the provoked PMs were depressed by urethan administered 1-5 days before the lavage of PMs. These functions of resident PMs (rPM) were not altered by the drug treatment. Urethan added to the cultures of resident or provoked PMs proved to be ineffective. These results led to the conclusions that urethan, after its in vivo metabolic conversion, causes an impairment of the macrophage functions in the inductive phase of the immune response and this event may be the crucial point in the immunosuppressive effect of urethan.