The IL-2 receptor beta subunit is absolutely required for mediating the IL-2-induced activation of NK activity and proliferative activity of human large granular lymphocytes.

TU27 monoclonal antibody reacts with the cellular receptor to the beta subunit of the interleukin-2 receptor (IL-2R) (p70-75). This reagent has been utilized to demonstrate directly that the IL-2R beta is the IL-2-binding protein that mediates the activation of large granular lymphocytes (LGL) to proliferate and increase cytolytic activity in response to IL-2. The results presented here show that (i) the frequency of TU27+ cells paralleled the frequency of CD16+ (Leu-11+) cells; (ii) TU27 completely abrogated the proliferative response of LGL to IL-2, while GL439, an anti-IL-2R alpha (anti-Tac) reagent, had a much smaller effect, and the effect of the two together was no different from the effect of TU27 alone; (iii) TU27 abolished the IL-2-induced activation of natural killer (NK) activity and inhibited the development of LAK activity, while GL439 had no effect; and (iv) TU27 also inhibited naive NK activity. Therefore, these data clearly show that the IL-2-IL-2R beta interaction is responsible, and probably completely so, for the proliferative and cytolytic-promoting effects of IL-2 on LGL. In addition, they also suggest a role for this interaction in autocrine effects on native NK activity.