A cloned chicken lymphokine homologous to both mammalian IL-2 and IL-15.
IL-2, cloned in several mammalian species, plays a critical role in immune system function. Indirect evidence suggests that IL-2-like molecules also exist in lower vertebrates, although none has been cloned. In view of the commercial importance of poultry and the lack of any IL-2 sequence data in lower vertebrates, we undertook to clone a chicken IL-2-like molecule. To this end, a cDNA library was constructed from activated chicken spleen cells and screened for T cell proliferative activity. Three clones of a single gene were isolated that produced a protein stimulatory for activated T cell blasts. This protein had 24 to 25% amino acid identity and 44 to 46% similarity to both bovine IL-2 and IL-15. The homology with IL-15 was unexpected, since primate IL-15 was reported to have no homology with IL-2. However, genetic distance analysis indicated that the chicken interleukin homology is closer to the mammalian IL-2 than to the mammalian IL-15 homology. Furthermore, the chicken gene has several characteristics of mammalian IL-2s: e.g., expression only by activated T cells, mRNA with a short 5' region preceding the open reading frame, and a short leader sequence. It has one characteristic that is unique to IL-15: four conserved cysteines allowing for two intrachain disulfide bonds.
Sundick
R S
RS
Department of Immunology and Microbiology, Wayne State University School of Medicine, Detroit, MI 48201, USA. rsundick@med.wayne.edu
Gill-Dixon
C
C
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002645:Chickens; D003001:Cloning, Molecular; D019409:Interleukin-15 / Q000235:genetics* / Q000276:immunology; D007376:Interleukin-2 / Q000235:genetics* / Q000276:immunology; D008322:Mammals; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D017385:Sequence Homology
D019409:Interleukin-15; D007376:Interleukin-2