| Abstract: | These studies analyze growth requirements for the normal γδ T cell population in peripheral lymphoid tissues. Avian γδ T cells can respond well to T cell mitogens in the presence of αβ T cells, but our studies indicate that they do not grow well alone. Exogenous growth factors were required in order for γδ T cells to proliferate in response to receptor ligation by anti-T cell receptor antibodies or other T cell mitogens. Interleukin-2 was implicated as one of the necessary growth factors that the γδ cells cannot produce adequately on their own. The response to dual stimulation (receptor ligation plus exogenous T cell factors) was attributable to a discrete subpopulation of γδ T cells that could be identified by their cell surface CD8, major histocompatibility complex class II expression and relative increase in cell size. Conversely, non-responsive γδ T cells did not exhibit these activation markers. These observations suggest a physiological basis for the relatively late appearance of γδ T cells in inflammatory responses and their failure as a population to match the growth potential of αβ T cells. More importantly, the results imply that the biological role of γδ T cells must be understood within the context of their interaction with αβ T cells. |
