GROWTH REQUIREMENTS FOR AVIAN GAMMA-DELTA-T-CELLS INCLUDE EXOGENOUS CYTOKINES, RECEPTOR LIGATION AND IN-VIVO PRIMING

These studies analyze growth requirements for the normal gammadelta T cell population in peripheral lymphoid tissues. Avian gammadelta T cel ls can respond well to T cell mitogens in the presence of alphabeta T cells, but our studies indicate that they do not grow well alone. Exog enous growth factors were required in order for gammadelta T cells to proliferate in response to receptor ligation by anti-T cell receptor a ntibodies or other T cell mitogens. Interleukin-2 was implicated as on e of the necessary growth factors that the gammadelta cells cannot pro duce adequately on their own. The response to dual stimulation (recept or ligation plus exogenous T cell factors) was attributable to a discr ete subpopulation of gammadelta T cells that could be identified by th eir cell surface CD8, major histocompatibility complex class II expres sion and relative increase in cell size. Conversely, non-responsive ga mmadelta T cells did not exhibit these activation markers. These obser vations suggest a physiological basis for the relatively late appearan ce of gammadelta T cells in inflammatory responses and their failure a s a population to match the growth potential of alphabeta T cells. Mor e importantly, the results imply that the biological role of gammadelt a T cells must be understood within the context of their interaction w ith alphabeta T cells.