DR antigen positive monocyte-macrophages control granulocyte-macrophage colony-stimulating activity and burst...

To investigate the mechanisms that modulate granulocyte-macrophage colony-stimulating activity (GM-CSA) and burst promoting activity (BPA) elaboration, we studied human peripheral blood-derived monocyte-macrophage (M0) and T-lymphocyte (TL) interaction. Coincubation of live M0 with autologous TL at a 1:3 ratio in the presence of 1% phytohemagglutinin synergistically increased GM-CSA (6 of 6 experiments) and BPA (4 of 6 experiments) (P less than 0.002). Prior treatment of M0 with cycloheximide or actinomycin D significantly (P less than 0.002) diminished this M0's capacity to collaborate with TL. Mitomycin C treatment did not. Live M0 also enhanced TL-derived GM-CSA (P less than 0.002) and BPA (P less than 0.001). This enhancement was again compromised by prior cycloheximide or actinomycin D treatment, but not by mitomycin C treatment. Further experiments in which we blocked DR antigen on M0 membrane with monoclonal anti-DR antibodies suggested that M0 required their membrane DR antigen to collaborate with TL in elaborating GM-CSA and BPA.