The role of fibroblastoid cells and macrophages from mouse bone marrow in the in vitro growth promotion of haemopoietic tumour cells.

Adherent cells from mouse bone marrow have been shown to promote the in vitro growth of the AVRij-1 tumour cell line. The experiments presented here suggest that the adherent cells involved in this phenomenon are the progeny of bone marrow derived fibroblastoid colony forming units. The latter were characterized by means of cell density distribution analysis. They had a broad distribution pattern and an average peak cell density of 1.069 g.cm-3. The growth promotion activity exerted by adherent cell layers from the various density fractions on the AVRij-1 tumour cell line coincided with the distribution of fibroblastoid colony forming units. On the other hand, the presence of macrophages in the adherent layers seemed to be non-essential for the in vitro promotion of growth of the AVRij-1 cell line.