The proliferative capacity of human T lymphocyte subpopulations in a continuous culture system

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Abstract
The continuous growth of subpopulations of human T lymphocytes was investigated using a culture system containing conditioning factors from mitogen‐stimulated lymphocytes. Cultures of purified peripheral blood lymphocytes rapidly became enriched for T lymphocytes, detected as sheep erythrocyte rosette‐forming cells, and could be maintained for up to a month in an actively growing state. Subpopulations of T lymphocytes bearing Fc receptors for IgM (T.M) or IgG(T.G) could not be detected in these cultures unless the cells were first washed and cultured for 3 days in medium devoid of conditioning factors. During this second culture step, many of the cells reverted from a large, blast‐like state to a small lymphocyte morphology and a proportion of the T lymphocytes re‐expressed Fc receptors. The proportions of T.M and T.G lymphocytes so detected remained constant throughout the continuous culture period indicating that the system permitted the proliferation of all T lymphocytes. Fractionation studies supported this conclusion by demonstrating that purified T, T.M and T.G but not B lymphocyte populations proliferated when cultured in the presence of conditioned medium. The majority of cells in cultures of purified T.M lymphocytes re‐expressed IgM Fc receptors following reculture in unconditioned medium. However, the re‐expression of IgG Fc receptors by cultured T.G lymphocytes could not be achieved.