| Abstract: | Long-term cultured T blasts with specificity for bovine insulin (BK-BI-1.2), which cease growing in IL 2 supplemented medium and require periodic antigenic challenge to resume proliferation, were selected as a model system to analyze the regulation of the growth of activated T cells. The use of AMT-13, a monoclonal antibody (mAb) directed at the murine IL 2 receptor, in indirect binding experiments and in FACS analysis allowed us to examine the time-dependent expression of IL 2 receptors on BK-BI-1.2 blasts after antigenic stimulation. The data reveal a transitory expression of IL 2 receptors, attaining maximal levels on day 2 after antigenic induction and having declined to low levels by day 6. mAb 10-2.16, reactive with I-Ak, did not inhibit T cell-proliferative capacity when the cells were subcultured in IL 2. This result suggests that, once induced to maximal levels by antigen, the transitory expression of IL 2 receptors on the descendent cells is not dependent on the continual presence of antigen-presenting cells. Thus, the progressive loss of IL 2 receptors apparently is not due to a mechanism operating by clearance of receptors from the cell surface on completion of each cell cycle, leading to dependency of the descendent cells on repeated contact with antigen for renewed receptor expression. The disappearance of IL 2 receptors from the surface of antigen-stimulated T cells might provide a basis for the control of immunologic specificity in vivo. |
