Fibroblasts mediate T cell survival: a proposed mechanism for retention of primed T cells.

This report describes a salvage pathway whereby activated T lymphocytes revert to nonproliferating cells in the absence of antigen or mitogenic signals. After the removal of mitogenic cytokines, cultured T lymphocytes cease dividing and rapidly begin to undergo cell death. However, the addition of fibroblasts to interleukin 2 (IL-2)-propagated T cells results in prolonged survival of the previously activated T lymphocytes in the absence of proliferation. The prevention of cell death is also achieved by conditioned medium from the fibroblasts. T lymphocytes cultured with fibroblasts or the conditioned medium retain the ability to be restimulated if mitogenic stimuli are added to the culture. The activity is not accounted for by IL-1-7. The studies suggest a stromal cell-mediated, nonspecific mechanism for survival of primed T lymphocytes in a nonproliferating state.