NK-lysin is an anti-microbial and anti-
tumor protein expressed by NK cells and T lymphocytes. In a previous report, we identified a set of overlapping expressed sequence tags constituting a contiguous sequence (contig 171) homologous to mammalian NK-lysins. In the current report, a
cDNA encoding
NK-lysin was isolated from a library prepared from chicken intestinal intraepithelial lymphocytes (IELs). It consisted of an 850 bp DNA sequence with an open reading frame of 140
amino acids and a predicted molecular mass of 15.2 kDa. Comparison of its deduced amino acid sequence showed less than 20% identity to mammalian NK-lysins. The tissue distribution of
NK-lysin mRNA revealed highest levels in intestinal IELs, intermediate levels in splenic and peripheral blood lymphocytes, and lowest levels in thymic and bursa lymphocytes. Following intestinal
infection of chickens with Eimeria maxima, one of seven Eimeria species causing avian
coccidiosis,
NK-lysin transcript levels increased 3-4-fold in CD4+ and CD8+ intestinal IELs. However, cell depletion experiments suggested other T lymphocyte subpopulations also expressed
NK-lysin. The kinetics of
NK-lysin mRNA expression indicated that, whereas
infection with E. acervulina induced maximum expression only at 7-8 days post-
infection, E. maxima and E. tenella elicited biphasic responses at 3-4 and 7-8 days post-
infection. Finally, recombinant chicken
NK-lysin expressed in COS7 cells exhibited anti-
tumor cell activity against LSCC-RP9, a retrovirus-transformed B-cell line. We conclude that chicken
NK-lysin plays important roles during anti-microbial and anti-
tumor defenses.