Inhibition of the blastogenic response of peripheral blood mononuclear cells to mitogen and antigens by bovine pulmonary macrophages and their culture supernatants.

Bovine pulmonary macrophages were shown to inhibit blastogenic response of peripheral blood mononuclear cells to high and low level stimulation with phytohaemagglutinin P. The blastogenic response of cells from calves sensitised to Pasteurella haemolytica or BCG, when stimulated with the corresponding antigen, was also suppressed by the addition of autologous pulmonary macrophages. Twenty-four-hour-old macrophage culture medium was likewise inhibitory to the blastogenic response. Determination of the arginine content of culture medium before and after 24 and 48 hours' incubation with macrophages showed a progressive decrease in arginine content. Dilution of the arginine deficient medium 1:16 with fresh culture medium did not reverse the inhibition, thus making arginine deficiency unlikely to account for the inhibition.