Cellular interactions between 3T3 cells and interleukin‐3‐dependent multipotent haemopoietic cells: A model system for stromal‐cell‐mediated haemopoiesis

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Abstract
With the aid of a multipotent stem cell line (FDCP‐mix cells) co‐cultured with either normal or irradiated Swiss 3T3, cellular interactions between stromal cells and haemopoietic stem cells were studied by electron microscopy and time‐lapse video microscopy. When cultured in the presence of interleukin 3 (IL‐3) but in the absence of stromal cells, the FDCP‐mix cells have a characteristic blast morphology. In the absence of IL‐3, the cells die unless they are co‐cultured with marrow stromal cells or 3T3 cells. In the latter case, they attach, proliferate, and differentiate on both normal and irradiated Swiss 3T3 cell layers without the addition of extrinsic growth factor (IL‐3). At the initial attachment sites of these two cell lines, cellular recognition seemed to be mediated by the formation of microvillus cytoplasmic projections and extracellular matrix. These areas may well be the sites of plasma‐membrane‐bound signalling/adhesional molecules between the interacting cells.