Effect of benzo[a]phenothiazines on natural killer cell activity of human peripheral blood mononuclear cells.

Four benzo[a]phenothiazines were investigated for their effects on antibody-dependent cellular cytotoxicity (ADCC) and natural killer (NK) cell and blast transformation of human peripheral blood mononuclear cells (PBM). Benzo[a]phenothiazines dose-dependently suppressed the nitrogen-stimulated T cell proliferation. The suppressive effect of non differentiation-inducing benzo[a]phenothiazines was higher than that of differentiation-inducing benzo[a]phenothiazines. The stimulation effect of differentiation-inducing compounds on the NK activity was reduced by removal of monocytes from the PBM. The results suggest the direct activation of monocytes (Mo) by differentiation-inducing benzo[a]phenothiazines.