Identification of the functional interleukin-2 binding domain of the chicken common cytokine receptor gamma chain

CD132 is the common gamma chain to a number of cytokine receptor complexes including that for IL-2. To identify the functional domain of chicken CD132 (chCD132), the cDNA of chCD132 was cloned, and a neutralizing monoclonal antibody, raised against a recombinant chCD132 protein, was identified by inhibition of IL-2-dependent proliferation of T cells. Flow cytometry analysis revealed that chCD132 molecules are expressed on the surface of splenic mononuclear cells. The functional domain of chCD132 that binds to chicken interleukin 2, Q84E94L95Q96N97L98, was found through phage display and peptide-competitive ELISA, and its critical residue Q96 was further identified. A tertiary structure model shows that the functional domain is positioned at the elbow-like junction of N and C terminal fibronectin-III domains of chCD132. These data provide experimental evidence for elucidating the interaction between chCD132 and chIL-2.