Participation of granulocytes in in vitro regulation of suppressor cell activity

In in vitro investigations factors were found in the specific granules of peripheral blood granulocytes of healthy subjects, which inhibited the induction of non-specific suppressor cells (S cells) in doses of 10 and 25 micrograms per 1 ml (1 X 10(6) cells) of 48-hour culture. In two-stage culture the S cells decreased the proliferation of responder lymphocytes (R cells) stimulated with Con A and pokeweed mitogen (PWM) by 56.8 +/- 2.4 per cent and 19.7 +/- 5.9 per cent, respectively. The above mentioned granulocyte factors (GF) caused a statistically significant reduction of S cell activity (p less than 0.01) or even its complete inhibition, depending on the mitogen stimulating the R cells (this inhibition was greater after stimulation of lymphocytes by PWM). Inactivation of proteolytic enzymes with di-isopropylfluorophosphate (DFP) failed to decrease the biological activity of these factors, which are released from the granulocytes after 30 minutes of granulocyte adherence to Petri dishes. Lymphocyte culture in a medium containing the supernatant from a culture of 1 X 10(6)/ml adherent granulocytes demonstrated increased proliferation of these lymphocytes and reduced activity of suppressor cells. On the other hand, an increase in the number of adherent granulocytes to 5 X 10(6)/ml of the medium produced a reverse effect: impairment of the proliferative response and enhancement of the activity of S cells.