The Differentiation of T Lymphocytes

Abstract

Dissociated mouse thymocytes were cultured under optimized conditions in Marbrook vessels in order to follow some aspects of T-cell differentiation. Under particular conditions it was possible to obtain a 50% net increase in the total number of the peripheral T-cell like, minor low Θ thymocyte subpopulation over the first day of culture, although this increase was lost with further incubation. The increase arose from proliferation of preexistent low Θ cells, and not from transformation of the major, high Θ population. Under all conditions the high Θ cells died rapidly in culture. These results are in accordance with the view that the high Θ and low Θ thymocytes represent separate streams of T-cell development. There was a striking increase in responsiveness to phytohemagglutinin and con-canavalin A after culture of thymocytes under these conditions. However, this was ascribed, not to the development of new immunocompetent T cells, but to selective cell death in the cultures eliminating some inhibitory elements. No increase in progenitors of cytotoxic lymphocytes was obtained. The results demonstrate some potential artifacts in assessing the immunocompetence of cultured thymocytes.

In vitro maintenance of differentiation marker synthesis by subpopulations of mouse thymocytes

“…This might be the result of selective cell death within each population, or the result of specific induction processes. Thymocytes displaying high levels of surface H-2 are known to enjoy a survival advantage in culture [20], and these are likely to be the cells that make H-2 K and D at the highest rate [ 7 ] . Even as a minor contaminant in the immature population, these cells would account for an increased share of overall protein synthesis in the culture after 24 h, leading to a relative enhancement of H-2 production.…”

“…In vivo, this is a specific marker for immature thymocytes [5,6,7,13] which, as a class, are poorly viable in culture [20]. Still, relative to the overall residual protein synthesis in these cultures, TdT synthesis actually accelerates.…”

Effect of human thymic epithelial conditioned medium on in vitro and in vivo alloantigen-induced lymphocyte activation in the mouse

“…So it is very likely that the enhancing effect of HTECM on the cytotoxic activity is not based on a selective survival of cytotoxic cells, but rather on the induction or multiplication of responsive cells. With respect to the latter possibility, Hopper et al (21) have reported that the absolute number of thymocytes expressing a low density of Thy-l antigen increased by about 50% during the first day of culture. These thymocytes represent the cortisone-resistant population, in which the cytotoxic T cells are found (8,9).…”