Identification of the functional domain of duck interleukin 2 binding to duck interleukin 2 receptor alpha chain.

Interleukin 2 (IL-2) plays an important role in the growth and differentiation of lymphocytes. To identify the functional domains of duck IL-2 (duIL-2), 4 neutralizing monoclonal antibodies (mAbs) to duIL-2 were used to finely map the functional domains of the duIL-2 protein. The mimotopes of 4 anti-duIL-2 mAbs, including LVXGSMPS, KPHKHHXHHSHM, WXXXKAKP, and HVPNERYPLR, were identified by phage display and peptide-competitive ELISA. These mimotopes constitute an important functional domain, Y(32) approximately T(44) (domain I), in the duIL-2 molecule. The bioactivity of the domain I peptide on in vitro lymphocyte proliferation was inhibited by duIL-2Ralpha. A tertiary structure model of duIL-2 showed that domain I is positioned in the long A-B loop and the N-terminal of Helix B. These data provided experimental evidence for elucidating the interaction between duIL-2 and duIL-2Ralpha.