Canine surface active material and pulmonary lymphocyte function. Studies with mixed-lymphocyte culture.

Canine bronchoalveolar cells, obtained by lavage, were enriched for lymphocytes by adsorption to plastic or by filtration over nylon wool and tested for their ability to function in the mixed lymphocyte culture (MLC) reaction. Pulmonary lymphocytes were markedly hyporesponsive to stimulation with allogeneic cells in vitro: their responses rarely exceeded 10% of those of blood lymphocytes obtained simultaneously from the same donor. However, pulmonary lymphocytes did function as stimulating cells, inducing allogeneic blood lymphocytes to proliferate in MLC. The failure of pulmonary lymphocytes to respond in MLC, coupled with their ability to stimulate clearly, distinguishes these cells from circulating blood lymphocytes. The effect of canine surface active material (SAM), a lipoprotein unique to the lung, on the function of blood lymphocytes in MLC was studied. A transient exposure to SAM in vitro profoundly suppressed blood lymphocyte responses to allogenic stimulation, but had only a minor effect on their function as stimulator cells in MLC. Thus, exposure to SAM in vitro converts normal blood lymphocytes into cells whose function mimics that of pulmonary lymphocytes. These results suggest that exposure of pulmonary lymphocytes to SAM in vivo may contribute to their abnormal immune reactivity in vitro.