Expression and role of interleukin‐2 receptor β chain on CD4−CD8+ T cell receptor αβ+ cells

Abstract

Using anti‐murine interleukin‐2 receptor β chain (IL‐2Rβ) monoclonal antibody (mAb), we have examined the expression of IL‐2Rβ on murine thymocyte subpopulations. We found that it was constitutively expressed on 1 %‐4% of thymocytes in an almost mutually exclusive fashion with IL‐2Rα. The expression of IL‐2Rβ is developmentally regulated. While it is expressed mainly on T cell receptor βδ⁺ (TcRγδ⁺) cells during fetal age, the major subpopulation expressing IL‐2Rβ in adult mouse shifts to CD4⁻CD8⁻TcR αβ⁺ thymocytes. A considerable portion of CD4⁻CD8⁻ TcR αβ⁺ cells in other organs, including spleen, bone marrow and liver, was also found to express IL‐2Rβ. In fetal thymus organ culture, the above thymocyte subset was induced to expand in response to exogeneous IL‐2, and the expansion was inhibited by addition of anti‐IL‐2Rβ mAb, suggesting that IL‐2Rβ is functional in this subpopulation. However, in vivo blockade of the IL‐2/IL‐2R pathway with the mAb did not exert any effects on the appearance of CD4⁻CD8⁻ TcR αβ⁺ cells both in the thymus and the periphery. This indicates that the development of CD4⁻CD8⁻ TcR αβ⁺ cells is not solely controlled by IL‐2 but also by other complex elements.