Functional and phenotypical characteristics of hepatic NK-like T cells in NK1.1-positive and -negative mouse strains

We previously reported and partially characterized a unique monoclonal antibody (mAb), U5A2-13, which recognizes a T cell subset similar to NK1.1(+) T cells, not only in NK1.1-positive mouse strains but also in NK1.1-negative strains. In NK1.1-positive C57BL/6 mice, U5A2-13(+) TCR alpha beta(+) cells produced abundant IL-4 as well as extremely high levels of IFN-gamma upon CD3 cross-linking, but this did not occur with U5A2-13(-) TCR alpha beta(+) cells. In NK1.1-negative C3H/He mice, U5A2-13(+) TCR alpha beta(+) cells produced high levels of IL-4 and IFN-gamma upon CD3 cross-linking, but this was not observed with U5A2-13(-) TCR alpha beta(+) cells. To the best of our knowledge, this is the first direct evidence of the presence of NK-like T cells defined phenotypically by U5A2-13 mAb and functionally by IL-4/IFN-gamma production in NK1.1-negative mouse strains. We also demonstrated that U5A2-13(-) NK1.1(+) T cells and U5A2-13(+) NK1.1(-) T cells in C57BL/6 mice could produce both IL-4 and IFN-gamma. In addition, V beta 8 or V beta 7 usage by U5A2-13(+) NK1.1(-) T cells was lower than that by U5A2-13(+) NK1.1(+) T cells, but remained higher than that by U5A2-13(-) NK1.1(-) T cells. Based on the present results, U5A2-13 mAb appears to be a valuable tool in the study of NK-like T cells.