Microbicidal property of B1 cell derived mononuclear phagocyte

A mononuclear phagocyte derived from B1b cells (B1CDP) has been described. As these cells migrate from the peritoneal cavity to non-specific inflammatory lesion sites and are highly phagocytic via Fc and mannose receptors, their microbicidal ability of these cells was investigated using the Coxiella burnetii cell infection model in vitro. In this report, the pattern of infection and C. burnetii phase II survival in B1CDP phagosomes was compared with the pattern of infection of peritoneal macrophages from Xid mice (PMφ) and bone marrow derived macrophages (BMMφ). Infection was assessed by determining the large parasitophorous vacuole formation, the relative focus forming units and the quantification of DAPI (4′,6-diamino-2-phenylindole) fluorescence images acquired by confocal microscopy. When compared to macrophages, B1CDP are more permissive to the bacterial infection and less effective to kill them. Further, results suggest that IL-10 secreted by B1 cells are involved in their susceptibility to infection by C. burnetti, since B1CDP from IL-10 KO mice are more competent to control C. burnetii infection than cells from wild type mice. These data contribute further to characterize B1CDP as a novel mononuclear phagocyte.