Human Post‐thymic Precursor Cells in Health and Disease

Abstract

Adult peripheral blood T lymphocytes activated in autologous mixed lymphocyte reactions (AMLR) exerted cytotoxicity on both phytohaemagglutinin-stimulated cells and Epstein-Barr virus-transformed cells. When autologous rosette-forming T cells were removed from total T lymphocytes, there was no generation of cytotoxicity. Re-addition of autologous rosette-forming T cells (Tar cells) to a population of T cells depleted of Tar cells restored the cytotoxic activity. T Treatment of Tar cells with mitomycin C before their activation in AMLR caused loss of their capacity to give rise to killer cells. Furthermore, resting Tar cells did not show any cytotoxic activity as determined in the two different types of target cells used. Since Tar cells are able to differentiate into T gamma cells and since T gamma cells possess spontaneous cytotoxic activity, it is likely that Tar cells participate in the generation of spontaneous killer cells in AMLR as precursors of cytotoxic effector cells.