Molecular and functional characterization of chicken IL-15

Abstract

A cDNA encoding chicken interleukin-15 was cloned from a CD4+ T cellhybridoma expression library by screening with a rabbit antibody against a protein fraction ofconditioned medium containing T cell growth promoting activity. The chicken IL-15 cDNAcontains an open reading frame of 143 amino acids with a single potential N-linked glycosylationsite. The predicted m.w. of the encoded protein [16]matched the size of animmunoreactive band on Western blots of E. coli expressing the recombinant IL-15.Amino acid and nucleotide sequence analyses of chicken IL-15 revealed 31% and 46% identitywith bovine IL-15 respectively and lesser homologies to other mammalian IL-15s. Chicken IL-15contained all 4 highly conserved cysteine residues present in mammalian IL-15 sequences.RT-PCR demonstrated that the chicken IL-15 gene is expressed in many tissues including spleen,intestine, and muscle and in established macrophage, T lymphoma and fibroblast cell lines.Activation of spleen cells with Con A enhanced the expression of IL-15 gene transcripts in atime-dependent manner. CHO-K1 cells transfected with the chicken IL-15 cDNA secreted abiologically active protein supporting the growth of Con A activated spleen lymphocytes.Continuous culture of spleen Con A lymphoblasts with chicken IL-15 over two months resulted inan enriched T lymphocyte population expressing the gdTCR, CD8a, and CD3 cell surfaceantigens.