NK-LYSIN, STRUCTURE AND FUNCTION OF A NOVEL EFFECTOR MOLECULE OF PORCINE NK-CELL AND T-CELL

NK-lysin (NKL), a 78-residue antimicrobial peptide, was isolated from pig small intestine. Standard methods identified the peptide as basic, with six half-cystine residues in three intrachain disulphide bonds. The sequence showed 33% identity with a part of a putative gene produc t (NKG5) from activated T and NK cells. NK-lysin showed antibacterial activity against Escherichia coli and Bacillus megaterium and marked l ytic activity against YAC-I, a NK sensitive tumour cell line, while sh eep red blood cells were unaffected. The cDNA clone corresponding to N K-lysin has been characterized. We have also analyzed the cell and tis sue specific expression and the induction of the gene. A lymphocyte fr action enriched in T and NK cells, stimulated by human interleukin-2 ( IL-2), showed a 30-fold increase of the NKL transcript. NK-lysin speci fic mRNA is also detectable in spleen, bone marrow and colon. Immunost aining showed NKL to be present in different types of lymphocytes. Our results strongly suggest that NK-lysin is involved in the inducible c ytotoxicity of T and NK cells.