Two distinct P70 interleukin-2 receptors on a murine large granular lymphocyte clone Y479

A continuous cloned cell line (Y479) was established by culturing normal mouse spleen cells in a high concentration of interleukin-2 (IL-2). Y479 cells showed morphological characteristics of large granular lymphocyte with the phenotypes of Thy-1.2+, T3+, Lyt-1-, Lyt-2-, L3T4-, B220-, AsGM1+, LFA-1+, and TcRV beta 8-. The Y479 cells required a high concentration of IL-2 for their growth but did not express detectable p55 IL-2 receptor (IL-2R) although they bound IL-2 with high and low affinities. Analysis of the IL-2 binding proteins on the Y479 cells revealed that both the high and low affinity receptors consisted only of 70 kDa protein. Analysis of the 70 kDa protein was performed using five monoclonal antibodies (L15, L20, L23, L34, and L61) against human recombinant IL-2. Although they recognized different epitopes, all monoclonal antibodies immunoprecipitated 70 kDa IL-2R that was cross-linked with radioiodinated IL-2. The supernatant after immunoprecipitation with L61 still contained IL-2/IL-2R complex that was L23-reactive, and the supernatant after immunoprecipitation with L23 contained L61-reactive IL-2/IL-2R complex, whereas L15 immunoprecipitated almost all the complex. Limited digestion of IL-2-cross-linked Y479 cells with trypsin caused the liberation of 45 kDa IL-2R fragment cross-linked with IL-2. This complex was immunoprecipitated by L15 or L61 but not by L23. These results suggest that there are at least two distinct 70 kDa IL-2R on the surface of Y479 cells.