PHAGOCYTOSIS AND ITS SIGNIFICANCE IN LEPTOSPIRAL INFECTION

Summary Macrophages and polymorphonuclear leucocytes phagocytosed Leptospita icterohaemorrhagiae in tissue culture. No differences were observed between the activities of phagocytes from guinea‐pigs (highly susceptible to infection with the strain of leptospira used), mice (moderately susceptible) or rabbits (resistant), nor between phagocytes from mimmunized and unimminized animals. Preliminary opsonization increased the initial rate of phagocytosis. Similar results were obtained in mouse peritoneal cavities. There was no evidence of cytotoxicity or of intracullular survival of leptospirae. It is unlikely that virulence or non‐specific resistance to infection is determined by phagocytosis; specific resistance is mediated by antibody insofar as it enhances phagocytosis by opsonization and agglutination.