T-cell colony formation from murine thymocyte subpopulations and pre-T cells

Murine thymocytes are able to proliferate on clonal basis as colonies in the semisolid medium methylcellulose. It has previously been shown that the colony-forming cells are predominantly rather mature thymocytes and presumably exclusively single positive CD8+ cells. The results of the present study point to that also immature CD4-CD8- (DN = double negative) thymocytes and pre-T cells from nude mice are able to form colonies in methylcellulose culture. The numbers of colonies are increased by the presence of phorbolester, and it is shown by the addition of various interleukins to the culture that IL-2 is the essential interleukin in colony formation. It is further shown that all colony cells derived from DN thymocytes are of the CD4-CD8+ phenotype, while nude mouse precursors give rise to either CD8+ or DN colony cells. Thus, no CD4+ T cells were able to proliferate as colonies by the present culture method, even after exposure to a number of different interleukins or phorbolesters. This makes the method a reliable tool for clonal growth of both immature and mature CD8+ thymocytes and T cells.