Characterization of murine CD160⁺ CD8⁺ T lymphocytes

CD160 is an Ig-like glycoprotein expressed on NK, NKT and TCRγδ T cells, as well as intestinal intraepithelial T lymphocytes. In addition, a minor subset of CD8⁺ but not CD4⁺ T cells in the periphery is also known to express CD160, but the subset has not been fully characterized. In this study, we prepared anti-murine CD160 mAbs and investigated the expression profile of CD160 on various subsets of CD8⁺ T cells. The amount of CD160 on almost all CD8⁺ T cells was increased upon CD3-mediated stimulation in vitro, and soluble CD160 was found to be released. Flow cytometric analysis revealed most CD8⁺ T cells expressing CD160 to show a CD44^high phenotype in vivo. On further analysis, both CD44^highCD62L^low effector memory T cells (T_EM) and CD44^highCD62L^high central memory T cells (T_CM) expressed CD160 at an intermediate level. High levels were evident with recently activated CD8⁺ T_EM. Naïve CD8⁺ T cells presumably immediately after stimulation (CD44^lowCD62L^lowCD69⁺) also expressed CD160, but only at a low level. Purified CD160⁺ CD8⁺ T cells from OT-1 transgenic mice expressing TCR against OVA residues 257-264 presented by H-2K^b produced IFN-γ more rapidly than CD160^- CD8⁺ T cells upon antigen stimulation. These results together show that CD160 is expressed on the majority of CD8⁺ memory T cells as well as recently activated CD8⁺ T cells.