Evidence for Two Subgroups of CD4−CD8− NKT Cells with Distinct TCRαβ Repertoires and Differential Distribution in Lymphoid Tissues

Abstract

NKT cells are a subset of T lymphocytes that is mainly restricted by the nonclassical MHC class I molecule, CD1d, and that includes several subpopulations, in particular CD4+ and CD4−CD8− (DN) cells. In the mouse, differential distribution of these subpopulations as well as heterogeneity in the expression of various markers as a function of tissue localization have been reported. We have thus undertaken a detailed study of the DN NKT cell subpopulation. With a highly sensitive semiquantitative RT-PCR technique, its TCR repertoire was characterized in various tissues. We found that mouse DN NKT cells are a variable mixture of two subgroups, one bearing the invariant Vα14 chain paired to rearranged Vβ2, Vβ7, Vβ8.1, Vβ8.2, or Vβ8.3 β-chains and the other exhibiting unskewed α- and β-chains. The proportion of these subgroups varies from about 100:0 in thymus, 80:20 in liver, and 50:50 in spleen to 20:80% in bone marrow, respectively. Finally, further heterogeneity in the tissue-derived DN NKT cells was discovered by sequencing extensively Vβ8.2-Jβ2.5 rearrangements in individual mice. Despite a few recurrences in TCR sequences, we found that each population exhibits its own and broad TCRβ diversity.