We investigated the effect of astromicin (ASTM) on a defence mechanism. The existence of ASTM (100 µg/ml) did not influence the ability of phagocytizing and killing by the mouse peritoneal exudated polymorphonuclear leukocyte (PMN). We observed no change of either phagocytizing and killing or phagocytizing ability of PMN by a pretreatment with ASTM (100 µg/ml). When the luminol-dependent chemilumines-cence of PMN was examined, a slight decrease of relative light intensity in the presence of ASTM was observed at a concentration of 100 µg/ml or 50 µg/ml. There was, however, no change of relative light intensity in the presence of 20 µg/ml of ASTM. The Chemotaxis of PMN was not influenced in the presence of even 100 µg/ml of ASTM. We also examined whether a combination effect existed between ASTM and either fresh human serum or fresh mouse serum in vitro. Considerable combination effects were observed against E. coli, P. aeruginosa, S. marcescens, K. pneumoniae and S. aureus. From these results, we concluded that ASTM did not exert a detrimental effect on examined functions of PMN which is important in the nonspecific host defence mechanism in the early phase of bacterial infections. We also concluded that ASTM, which had a synergic effect with a human serum factor, was a safe and effective chemotherapeutic agent.
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