Augmentation of the phagocytic activity of murine spleen cell populations induced by Adriamycin

C57B1/6 mice were injected i.v. with Adriamycin (5 mg/kg) and various days later, spleen cells were tested for Fc dependent phagocytic activity by measuring protection of 51Cr-labelled, antibody coated SRBC from hyptonic shock. No difference in phagocytic activity was observed with spleen cells from untreated mice or mice treated with Adriamycin 1-7 days prior to killing. Increases in phagocytic activity were, however, seen with spleen cells from mice treated 9 to 13 days prior to killing. Phagocytic activity of spleen cells from mice treated 5 days prior to killing was increased after these cells were cultured for 5 days when compared to cultured cells from untreated mice. Despite depletion of mature phagocytic cells from spleen cells suspensions by silica treatment, followed 24 hours later by silica removal by density gradient centrifugation, phagocytic activity was observed with spleen cells from ADM treated mice (day-5) after 5 days in culture. No phagocytic activity was seen with spleen cells from untreated mice using the same silica treatment and culture conditions. When cultured spleen cells from untreated or ADM treated mice (day-5) were fractionated by plastic adherence, twice as many adherent cells were removed compared to controls. Their phagocytic activity (per cell) was, however, the same. Thus, ADM may increase the number of immature nonphagocytic macrophages in the spleen resulting in increased mature macrophages after culture.