Characterisation and expression analysis of the chicken interleukin-7 receptor alpha chain

Interleukin-7 (IL-7) is a central regulator of T cell survival and homeostasis and its expression is indicative for naïve and memory T cells. We cloned chicken IL-7Ralpha (CHIL-7Ralpha) and determined its expression profile in chicken lymphocyte subpopulations. The predicted protein sequence contained 460 amino acids. The extracellular domain exhibited features typical of a type I cytokine receptor; a fibronectin type III domain and the GXWSXWS motif were conserved. ChIL-7Ralpha mRNA is highly expressed in lymphoid organs and in CD4+, CD8alpha+ and CD8beta+ cells. A monoclonal antibody was generated and expression of the protein investigated. ChIL-7Ralpha was expressed on CD4+ and CD8alpha+, but not CD8beta+, T cells, in contrast to the high mRNA expression levels in all of these cells. Upon polyclonal stimulation with ConA, IL-7Ralpha was rapidly down-regulated on T cells, suggesting that in the chicken expression of this receptor might also be correlated to the T cell activation status.