IL-2 Receptor α-Chain Expression Is Independently Regulated in Primary and Secondary Lymphoid Organs

Abstract

Abstract The IL-2R is composed of three chains: IL-2Rα, IL-2Rβ, and IL-2Rγ. In mice, IL-2Rα is critical and determines IL-2 binding to the tripartite IL-2R complex. To extend our previous studies, which demonstrated that IL-2 regulates IL-2Rα expression in vitro, we have analyzed expression in IL-2-deficient mice in vivo. As in control animals, CD4−CD8− thymocytes and bone marrow-derived B220+ pre-B cells were Il-2Rα positive. In contrast, activated lymph node and splenic CD4 T cells (CD4+CD69+) were found to be IL-2Rα negative, whereas ∼20% of the same cell populations from the MLR/lpr strain, which also accumulate large numbers of CD4-activated T cells in the presence of intact IL-2, retained expression. A similar pattern of IL-2Rα expression was found among splenic CD8 cells from IL-2−/− and IL-2+/− animals. These findings demonstrate that in primary lymphoid organs, IL-2 is not directly involved in IL-2Rα expression. However, at the level of mature lymphocytes, and more specifically CD4 T cells, IL-2 remains in vivo, as in vitro, the most critical cytokine controlling both IL-2Rα expression and sensitivity to IL-2.