Induction of human T-lymphocyte colonies by phorbol myristate acetate

Colony growth of human lymphocytes by phorbol myristate acetate (PMA) was studied. PMA was able to induce lymphocyte colony growth in methylcellulose semi-solid cultures in the absence of lectin mitogens, phytohaemagglutinin or concanavalin A. PMA-induced colonies were found in cultures of mononuclear cells, monocyte-depleted mononuclear cells and the T-enriched cell fraction, whereas no colonies were obtained from the non-T cell fraction. At least one million mononuclear cells were required to form colonies by PMA. The colony cells were mainly T cells as judged from sheep red blood cell rosette formation. Surface immunoglobulin positive cells and peroxidase positive cells were not detected in colony cells. Non-specific esterase positive cells were only found to be less than 1% of colony cells. T cells formed more colonies than did mononuclear cells, presumably because of a concentration of colony forming cells and/or co-operating cells. Colony formation by PMA was induced from monocyte-depleted mononuclear cells and monocyte-depleted T cells, suggesting independence of monocytes. When mononuclear cells were precultured at 37 degrees for 5 min or 30 min with PMA and then cultured in the semi-solid medium without PMA, only a small number of colonies grew. Further studies of PMA-induced T-cell colonies will provide information the identification and characterization of immunological states in various immunological diseases.