Effects of retinoids on human lymphocyte functions in vitro.

E-Rosette formation in vitro, lymphocyte mitogenesis and natural killer (NK) activity of human blood lymphocytes were strongly inhibited by high concentration (10(-4) M) of retinol or retinal. Other retinoids at 10(-4) M (retinoic acid and 13-cis-retinoic acid) and lower concentrations (10(-7) or 10(-9) M) of retinol, retinal and carotenes also inhibited E-rosette formation. Lymphocyte transformation responses induced by concanavalin A (Con A) or pokeweed mitogen (PWM) were also inhibited while NK activity was not affected. There was a remarkable depression of the total number of viable lymphocytes after incubation with retinol or retinal 10(-4) M. However, other retinoids, 10(-7) and 10(-9) M of retinol and retinal and carotenes did not show marked decrease of lymphocyte number or viability even after prolonged incubation (48 h). The mechanism of inhibition by retinol or retinal (10(-4) M) is due in part to the decrease of viable lymphocytes. It is unclear how other retinoids, carotenes and lower concentrations (10(-7) or 10(-9) M) of retinol or retinal inhibit E-rosette formation or lymphocyte transformation.