Vα14+ NK T cells: A novel lymphoid cell lineage with regulatory function

Abstract

A novel lymphoid lineage, NK T cells, was recently found. The NK T cells are the major population in the periphery comprising 5% of splenic T cells and 40% of bone marrow T cells. They express a unique TCR composed of invariant Vα14Jα281 and Vβ8.2 together with NK receptor (NKRPI). Surprisingly, the invariant Vα14+ TCR is exclusively expressed on NK T cells but not on conventional T cells. As the selective decrease in Vα14+ NK T cell population in the periphery is tightly correlated with autoimmune disease development, Vα14+ NK T cells control development of autoimmune diseases. We also found that Vα14 TCR gene rearrangement and transcripts were detected at an early embryogenesis (d9.5) before the thymus formation. Therefore NK T cells are in the distinct category from conventional T cells. The target of NK T cells is found to be CD1 (class 1b, monomorphic class I MHC-like molecule) present on bone marrow–derived cells and is killed by Fas-FasL interaction or perforin-mediated mechanisms. These results indicate that NK T cells consist of an immunoregulatory system different from defense system in terms of homogeneous repertoire, extrathymic development in early stage of gestation, and their regulatory functional role. (J Allergy Clin Immunol 1996;98:S263-9)