Conagenin derived from Streptomyces roseosporus enhances macrophage functions

In contrast to the studies that describes the effects of conagenin (CNG) on the cellular immunity of lymphocytes (references), we investigated the in vitro effect of CNG on macrophage function. Phagocytosis of alveolar macrophages (AM) against opsonized-sheep red blood cells (SRBC) was significantly enhanced following in vitro incubation with CNG for 12 hours at 37 degrees C, which was closely associated with increased expression of Fc-receptor in AM membranes. Macrophage-activating factor (MAF), prepared from splenic lymphocytes in vitro stimulated with concanavarin A (Con A) for 48 hours at 37 degrees C, had also the enhancing effect on phagocytosis of AM against opsonized-SRBC. Preincubation with CNG (0.1 microg/ml) and MAF (1/100 dilution) induced the additional effect on phagocytosis of AM, which was associated with the increased expression of Fc-receptor in AM membranes. These results suggest that CNG enhances AM phagocytosis by increasing the expression of Fc-receptor on their membranes via either effecting different sub-populations of AM cells or by activating independent mechanism on the same AM cell population.