FIGURE 2.

IL-15Rα containing Ex2A is functional. A, chimeric proteins comprising human IL-15Rα with or without the Ex2A domain and an Fc portion of human IgG1 were co-expressed with IL-15 in 293 cells, and the resulting supernatants were analyzed by ELISA with plate-bound anti-Fc antibodies and soluble antibodies recognizing Ex2A, IL-15Rα, or IL-15. Although the presence of Ex2A appeared to decrease secretion levels, heterodimers were detected by antibodies against both IL-15Rα and IL-15, suggesting that the binding of IL-15 to IL-15Rα was not affected by Ex2A. B, exposure of human NK cells from healthy donors to the same supernatants caused proliferation rates that were equivalent to the amounts detected by ELISA. This suggests that a presence of the Ex2A domain did not inhibit the proliferation-inducing activity of the IL-15/IL-15Rα complex.