Comprehensive gene expression analysis of human NK cells and CD8+ T lymphocytes

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Abstract
Cytotoxic lymphocytes, NK cells and CD8+ T cells play a pivotal role in the host defense. To reveal the biological function of these cells through establishing a comprehensive gene expression profile, serial analysis of gene expression was performed in human peripheral blood NK cells and CD8+ T cells. In total, 85,848 tags corresponding to >20,000 different transcripts were sequenced. The genes expressed abundantly in these libraries mostly consisted of genes encoding MHC class I and molecules related to protein synthesis. Among gene transcripts which related to cytotoxicity, granulysin, perforin, granzyme B and α‐defensin 1 were highly expressed in NK cells. Resting CD8+ T cells did not express the genes related to cytotoxicity, but expressed abundantly the genes encoding chemokines, tumor necrosis factor family. When CD8+ T cells were sorted into naive, memory and effector subsets based on the expression of CD45RA and CD27, perforin and granzyme B were expressed in the CD45RA+CD27– effector subset. α‐Defensin 1, one of the selectively expressed genes in NK cells, induced migration of naive CD8+CD45RA+CD27+ T cells, but not memory CD8+CD45RA–CD27+ or effector CD8+CD45RA+CD27– T cells. Furthermore, treatment with IL‐15, a stimulator of NK cell development, differentiation, survival and cytotoxicity, rapidly enhanced the expression of α‐defensin 1 in NK cells. The identification of the genes preferentially expressed in NK and CD8+ T cell subsets may give important insights into the functions of these cells against virus infection and in tumor immunity.