Functional properties of intra-epithelial lymphocytes from mouse small intestine. IV. Investigation of the proliferative capacity of IEL using phorbol ester and calcium ionophore.

Intra-epithelial lymphocytes (IEL) from mouse small intestine normally show very poor proliferative responses to mitogens or antigens in vitro. In this report, we show that purified IEL give a moderate proliferative response when stimulated with a combination of phorbol myristate acetate (PMA) and the calcium ionophore, A23187. Nevertheless, the response of IEL to these agents was much less than that of other lymphoid cells, even when stimulated additionally with concanavalin A (Con A). Furthermore, in comparison with spleen cells, the optimal response of IEL to PMA required higher concentrations of A23187. Optimally stimulated IEL made significant amounts of T-cell growth factor and addition of rIL-2 to the cultures did not enhance the optimal response of IEL to PMA + A23187. Subsequent studies showed that the majority of IEL which respond to PMA + A23187 are L3T4+ Lyt-2-, despite the fact that Lyt-2+ cells from the spleen and thymus responded well to these agents. Our study indicates that the majority of IEL have a very low proliferative potential in vitro and this may reflect a large population of IL-2-unresponsive Lyt-2+ IEL.