INVITRO MAINTENANCE OF BONE MARROW-RESIDENT T-CELL PRECURSORS IN CULTURES SUPPLEMENTED WITH EXOGENOUS IL-3

T cell precursors (pre-T cells) from adult murine bone marrow were propagated in vitro using a newly developed cell culture system. This system differs from "classical" bone marrow culture techniques in that it does not require the establishment of a monolayer of bone marrow stromal cells nor the presence of an irradiated feeder layer for the maintenance of the pre-T cell compartment, but rather depends on the continuous presence of exogenous interleukin-3 (IL-3) in the culture. Cells harvested from these cultures retain the capacity to repopulate the thymuses of sublethally irradiated recipient mice, following intrathymic transfer, for at least 2 weeks after the initiation of the cultures. Interestingly, pre-T cells maintained under these culture conditions rapidly lose their capacity for thymic repopulation following intravenous transfer, suggesting a potential defect in recirculation and/or homing properties. This culture system should prove useful in the investigation of bone marrow-resident pre-T cells. © 1990.