The regulatory role of macrophage factors on rat lymphocyte reactivity

The sensitized peritoneal rat macrophages released in vitro soluble factors stimulating and transforming normal syngenic lymphocytes into the cytotoxic cells with nonspecific activity. Normal peritoneal macrophages released factors stimulating a low spontaneous synthesis of DNA in lymph node lymphocytes or suppressing a high spontaneous synthesis of DNA in native and cortisone-resistant thymocytes. Normal lymph node macrophages in addition to factors suppressing the spontaneous synthesis of DNA in native and cortisone-resistant thymocytes also release factors enhancing or depressing the response of lymphocytes to PHA; the revealing of one of the opposite activities was dependent on the rate of lymphocyte stimulation with PHA. The factors released by lymph node macrophages could also reconstitute the reactivity of lymphocytes depleted of adherent cells to PHA.