Phagocytic properties of bone marrow fibroblasts.

Phagocytic activity has been observed in cultured marrow derived adherent cells (MDAC). Characterization studies indicate that these populations consist largely of collagen-producing fibroblasts, having failed to reveal markers associated with mononuclear phagocytes (MNP). Phagocytic activity by MDAC was therefore investigated. Characterization studies again failed to demonstrate an Fc receptor and confirmed that human MDAC synthesize collagen in vitro. Phagocytic activity against polystyrene microspheres was observed in 40% of MDAC. Control studies using P-8 and WI-38 fibroblasts yielded similar results. MDAC, P-8 and WI-38 fibroblasts were exposed to fluorescent microspheres and subsequently stained by immunofluorescence for type I collagen. Many cells were seen both to contain fluorescent particles and to stain positively for type I collagen. These results indicate that marrow derived fibroblasts, in common with fibroblasts from other sources, have phagocytic capability under appropriate conditions.