ALVEOLAR MACROPHAGES .2. INHIBITION OF LYMPHOCYTE-PROLIFERATION BY PURIFIED MACROPHAGES FROM RAT LUNG

Abstract

Macrophages were prepared from the lung, peritoneal cavity and blood of normal, unstimulated rats from a number of strains. The macrophages were purified by adherence and characterized via surface markers, enzyme activity and phagocytic capacity, and subsequently tested for activity in cultures of mitogen-stimulated syngeneic lymphocytes. Peritoneal macrophages and blood monocytes were mildly stimulatory, or ineffective in modulating mitogen-induced DNA synthesis; peritoneal macrophages reconstituted the blastogenic responses of macrophage-depleted lymph node cell cultures to normal limits. Alveolar macrophages were markedly inhibitory to lymphocyte proliferation; in some instances inhibitory activity was demonstrable when added alveolar macrophages comprised only 0.04% of the total cells in culture. Lymphocyte proliferation induced by T[thymus derived]-cell mitogens was more susceptible to this inhibition than was proliferation induced by the B[bone marrow derived]-cell mitogen LPS [lipopolysaccharide]. Alveolar macrophages recovered from SPF [specified pathogen free] rats, while less in number, exhibited comparable inhibitory activity. These results form part of an emerging picture of the normal alveolar macrophage as a potential suppressor of T-cell in the lung.