Suppression of mitogenic lectin-induced blast transformation of human peripheral blood mononuclear cells by pyrimethamine.

The anti-malarial drug pyrimethamine suppresses in vitro mitogenic lectin-induced blast transformation by human peripheral blood mononuclear cells (MNC) when the drug is added to cells (1 X 10(-5) M/culture). Sulphadoxine, a second widely used anti-malarial drug has no suppressive effect on the MNC. MNC responsiveness in the mixed leucocyte reaction and cellular viability are not altered by either pyrimethamine or sulphadoxine. In addition, no significant suppression is found when serum obtained from individuals on pyrimethamine-sulphadoxine chemoprophylaxis is added to MNC in the assays. The data, however, do not totally rule out any clinically significant suppressive effect by the anti-malarial drugs on human cellular immune responses.