Functional deficiencies of peritoneal cells from gene-targeted mice lacking G-CSF or GM-CSF

Gene-targeted mice lacking the hemopoietic growth factors, granulocyte colo ny-stimulating factor (G-CSF) or granulocyte-macrophage (GM)-CSF, show incr eased susceptibility to infection with, the facultative intracellular bacte rium, Listeria monocytogenes. The resident peritoneal cell populations from G-CSF-/- and GM-CSF-/- mice showed reduced production of the bactericidal molecule nitric oxide. Macrophage-mediated tumoricidal activity and phagocy tosis of Listeria were reduced in G-CSF-/-, but not in GM-CSF-/-, mice. In G-CSF-/- mice, there Tvas an unexpected expansion (from 18% in WT to 38%) o f a population of cells with morphology intermediate between typical macrop hages and typical lymphocytes. These cells had some of the features of poor ly differentiated macrophages, being adherent to plastic but poorly phagocy tic, nonspecific esterase positive but myeloperoxidase negative. They were largely negative for the macrophage marker F4/80 and for Thy1, B220, and Gr 1. Their disproportionate presence, and the corresponding deficiency in typ ical macrophages, possibly accounts for some of the functional deficiencies observed in G-CSF-/- mice.