Suppressor activity of T cells bearing Fc receptors for IgG on lymphoid colony formation.

Human T lymphocytes, upon phytohaemagglutinin stimulation, are able to form colonies in semisolid media. Peripheral T cell bearing Fc receptors (TG) were studied for their possible regulatory activity on lymphoid colony development. Although no substantial differences were observed between the cloning efficiency of unfractionated T cells (thus including TG cells) and T cells depleted of TG, a sharp suppression of colony formation occurred when positively selected TG cells were readded to TG-depleted suspensions. Therefore, TG suppressor activity seems to be strictly dependent upon cell interaction with ox IgG immune complexes used for TG cell isolation. Different experimental approaches failed to demonstrate, although did not exclude, that suppression in this system is mediated by soluble factors. gamma-irradiation of TG cells abrogated their suppressor capacity.