Evaluation of antigen presentation by a murine Ia+ T-cell clone, BK-BI-2.6.C6.

The capacity of cloned murine Ia-positive BK-BI-2.6.C6 T cells to present protein antigens to antigen-reactive long-term cultured T-cell lines was investigated. Antigen recognition by T-line cells on presenting BK-BI-2.6.C6 T-accessory cells resulted in efficient production of lymphokines. While antigen-dependent T cells with transient interleukin-2 receptor (IL-2R) expression were not induced to proliferate, T cells with constitutive IL-2R expression proliferated in response to the secreted IL-2. Although antigen presentation by BK-BI-2.6.C6 T cells resulted in a slight induction of IL-2R expression on responding T cells, as measured by flow cytometry, this augmentation was much smaller than that induced by antigen-presenting spleen cells. Thus the inability of antigen-presenting T-accessory cells to stimulate proliferation of responding T cells with transient IL-2R expression appears to reflect a lack of signal(s) necessary for the induction of IL-2R up to a level critical for initiation of cell division. This test system represents an ideal model to investigate the nature of signals required, in addition to triggering of the T-cell antigen receptor, for the induction of IL-2R.