Comparison of the colony-forming capacities of human T-lymphocyte subpopulations

Purified human peripheral blood T cells were fractionated into cells with IgM receptors (T_M) or IgG receptors (T_G) or "null" cells, i.e., cells without detectable Fc μ and Fc γ receptors (T null), and tested for colony formation in semisolid medium in the presence of PHA. T_G cells formed only a few colonies, T_M cells had the same efficiency as unfractionated T lymphocytes, while the T null fraction consistently showed the highest cloning capacity. The addition of adherent cells (AC) enhanced the cloning efficiency of purified T cells and of all of the subsets. However, the presence of AC was not a strict requirement for colony induction nor did it eliminate the observed differences in the colony-forming capacities of the various subsets.