Expression of the macrophage-specific antigen F4/80 during differentiation of mouse bone marrow cells in culture.

Abstract

The expression of the mouse macrophages (.vphi.)-specific antigen (Ag) F4/80 during in vitro differentiation was studied. The progenitor cells, the colony-forming unit in culture and cluster-forming cell, lacked Ag F4/80 but gave rise to colonies of F4/80-positive adherent m.vphi., as shown by fluorescence-activated cell sorting and clonal assays with L cell-conditioned medium as the source of growth factor. Ag F4/80 first appeared on a nonadherent precursor found in mass liquid BM (bone marrow) cultures after 3 days. Once adherent, m.vphi. expressed high levels of Ag F4/80 and other markers. The role of L cell-conditioned medium and of adherence on expression of Ag F4/80 was also examined. Clonal analysis of F4/80 and the Mac-1 and 2.4G2 (FcR) antigens showed that all cells in all independent colonies come to express these markers. F4/80 is apparently a marker for the more mature stages of m.vphi. development. Ag expression evidently increases progressively during maturation in vitro. Heterogeneity of Ag expression can be ascribed to variation in development and not to independent subsets of the m.vphi.