EFFECT OF GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR ON THE NUMBER OF LEUKOCYTES AND COURSE OF LISTERIA-MONOCYTOGENES INFECTION IN NAIVE AND LEUCOCYTOPENIC MICE

This study concerns the effect of recombinant murine granulocyte-macro phage colony-stimulating factor (GM-CSF) on the number of circulating leucocytes, activation of peritoneal macrophages and proliferation of Listeria monocytogenes in various organs of naive and leucocytopenic m ice. Mice were rendered leucocytopenic by sublethal total body irradia tion or cyclophosphamide treatment. GM-CSF treatment enhanced the numb er of granulocytes and monocytes in peripheral blood during L. monocyt ogenes infection in naive mice, but not in irradiated or cyclophospham ide-treated mice. In naive mice, irradiated and cyclophosphamide-treat ed mice, GM-CSF did not affect the course of L. monocytogenes infectio n in thigh muscle, spleen and liver. However, GM-CSF treatment signifi cantly increased the number of macrophages in the peritoneal cavity of naive mice during infection; these macrophages were more enlarged and showed a higher frequency of binucleated and multinucleated cells rel ative to non-GM-CSF-treated mice. Together, these results demonstrated that GM-CSF increased the number of circulating granulocytes and mono cytes, and the number of peritoneal macrophages during infection with L. monocytogenes in naive mice, but did not affect the course of the i nfection in thigh muscle, spleen or liver of these mice. In leucocytop enic mice, however, GM-CSF did not affect the number of circulating ph agocytes, which explains that this factor had no effect on the prolife ration of the bacteria in the various organs.