PHA-induced human T cell colony formation: enhancing effect of large granular lymphocytes.

The capacity of phytohemagglutinin (PHA)-stimulated human T cells to develop into colonies in agar has been evaluated in the presence or absence of a variety of peripheral blood mononuclear cell subsets. A subpopulation of non-T, non-B cells with receptors for the Fc portion of IgG (i.e. third population cells or TPC) was found to enhance considerably the T cell colony forming capacity. Since TPC have been previously shown to be highly enriched for large granular lymphocytes (LGL, i.e. cells with cytoplasmic azurophilic granules and acid hydrolases), LGL were purified on Percoll density gradients and tested for their T cell colony enhancing capacity. It was shown that LGL were indeed the cells capable of enhancing the T cell colony formation.