Sensitivity of preincubated lymphocytes to suppressor regulation.

DNA synthesis of human peripheral blood lymphocytes increases if Con A is added to the culture after 24 h preincubation at 37 degrees C. During preincubation the mitogen reactive lymphocytes lose their sensitivity to the suppressive effect of autologous mitomycin-treated mononuclear leukocytes, and of supernatants of autologous preincubated cells. The reactive lymphocytes preincubated at 4 degrees C retain their sensitivity to the suppressive effect of regulatory cells and their supernatants. It is assumed that the enhancement of mitogen response after preincubation at 37 degrees C is caused by a decrease of suppressor regulation of human lymphocytes. Prostaglandins may be regarded as one of the mediators of the suppression.