Phagocytic functions of pulmonary alveolar macrophages in genetically selected lean and obese swine and the effects of exogenous linolenic acid upon cell function.

Alveolar macrophages from genetically selected obese and lean swine were compared for in vitro phagocytic capabilities, using Fc (gamma)- and C3-mediated phagocytosis. Cells from obese pigs were significantly more effective at Fc (gamma)-mediated phagocytosis than those from lean pigs, both for percentage of total cells phagocytosing (P less than 0.044) and for the average number of opsonized sheep erythrocytes (SRBC) ingested per phagocyte (P less than 0.045). A seasonal interaction was noted for average number of SRBC ingested per phagocyte: the relative difference in macrophage responses between obese and lean groups became significantly more pronounced during winter and spring months (P less than 0.080). Macrophages from obese pigs also exhibited higher phagocytic activities at C3-mediated phagocytosis than did cells from lean pigs, but these differences were significant only for average number of SRBC ingested per phagocyte (P less than 0.080). Exogenous linolenic acid was added to selected cultures undergoing Fc (gamma)-mediated phagocytosis. Addition of the fatty acid frequently caused enhanced phagocytosis. Macrophages from obese pigs were stimulated by fatty acid treatment more frequently than cells from lean pigs (P less than 0.05). Relatively greater enhancement was also seen in cells from obese pigs, when compared with those from lean swine (P less than 0.025). These results suggest that genetically transferred factors are of primary importance in alveolar macrophage phagocytic responses and that linolenic acid can induce increased phagocytic activity by porcine alveolar macrophages in vitro.