Interaction between lymphocytes and inflammatory exudate cells. I. Enhacement of thymocyte response to PHA by product(s) of polymorphonuclear leukocytes and macrophages.

Thymocytes of C3H/He mice were poorly triggered to induce DNA synthesis by phytohemagglutinin but fairly well triggered when they were mixed with small number oble product(s) of these cells. Peritoneal exudate cells were mainly harvested at 3 hr, largely consisting of macrophages, after intraperitoneal injection of 0.2% sodium caseinate. Addition of 2(2) to 2(6) x 10(3) of 3-hr exudate cells, 2(2) to 2(4) x 10(3) of 48-hr exudate cells, or 2(2) to 2(4) x 10(3) of 96-hr exudate cells to syngeneic thymocyte culture (3 x 10(6) resulted in marked enhancement of DNA synthesis by thymocytes stimulated with 1 mul PHA. Similar enhancement of DNA synthesis was also observed in the presence of 200 mul of cellfree supernatant fluid of peritoneal exudates of 3 hr or 9 hr after casein stimulation. Conversely, two hundred microliters of 0-hr, 48-hr, or 96-hr peritoneal fluid showed a slight suppressing effect on thymocyte response and 50 to 100 mul of these exudates showed no enhancing effect. Furthermore, 50 to 800 mul of culture supernatants from 1.6 x 10(6) cells/4 ml of 3-hr exudate cells, 96-hr exudate cells, or purified macrophages also caused a similar enhancement of DNA synthesis by thymocytes. On the other hand, excess numbers of exudate cells (2(7) to 2(8) x 10(3) of 3-hr exudate cells, or 2(5) to 2(9) of 96-hr exudate cells) or excess amounts of culture supernatants (800 mul from 6.4 to 12.8 x 10(6)/4 ml of 3-hr cells, or 200 mul from 12.8 x 10(6)/4 ml, 400 mul from 6.4 x 10(6)/4ml, or 800 mul from 3.2 x 10(6)/4 ml of 96-hr cells) diminished the enhancing potency on thymocytes. The cooperative function by polymorphonuclear leukocytes or by macrophages on the lymphocyte response was thus postulated.