Evidence for two subgroups of CD4-CD8- NKT cells with distinct TCRαβ repertoires and differential distribution in lymphoid tissues

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 V alpha 14 chain paired to rearranged V beta2, V beta7, V beta8.1, V beta8.2, or V beta8.3 beta -chains and the other exhibiting. unskewed alpha- and beta -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 V beta8.2-J beta2.5 rearrangements in individual mice. Despite a few recurrences in TCR sequences, we found that each population exhibits its own and broad TCR beta diversity.