Human bone marrow fibroblast colony-forming units (CFU-F).

The bone marrow population includes a cell type which is able to give rise in vitro to fibroblast colonies (CFU-F). CFU-F are adherent, nonphagocytic, nonproliferating, relatively radioresistant, Ia antigen-negative cells having a wide density and sedimentation rate distribution. CFU-F frequency in normal bone marrow (aspirates) is 68 +/- 10 (range: 40-143; n = 10), per 5 X 10(6) cells. The fibroblastic nature of CFU-F progeny is demonstrated by immunofluorescent staining with anti-type I and anti-type III collagen, which are components of the marrow intercellular space and known to be produced by fibroblasts.