MHC class I target recognition, immunophenotypes and proteomic profiles of natural killer cells within the spleens of day-14 chick embryos.

Chicken natural killer (NK) cells are not well defined, so little is known about the molecular interactions controlling their activity. At day 14 of embryonic development, chick spleens are a rich source of T-cell-free CD8αα(+), CD3(-) cells with natural killing activity. Cell-mediated cytotoxicity assays revealed complex NK cell discrimination of MHC class I, suggesting the presence of multiple NK cell receptors. Immunophenotyping of freshly isolated and recombinant chicken interleukin-2-stimulated d14E CD8αα(+) CD3(-) splenocytes provided further evidence for population heterogeneity. Complex patterns of expression were found for CD8α, chB6 (Bu-1), CD1-1, CD56 (NCAM), KUL01, CD5, and CD44. Mass spectrometry-based proteomics revealed an array of NK cell proteins, including the NKR2B4 receptor. DAVID and KEGG analyses and additional immunophenotyping revealed NK cell activation pathways and evidence for monocytes within the splenocyte cultures. This study provides an underpinning for further investigation into the specificity and function of NK cells in birds.