EXPANSION OF NATURAL (NK1(-CELLS THAT EXPRESS ALPHA-BETA-T-CELL RECEPTORS IN TRANSPORTERS ASSOCIATED WITH ANTIGEN PRESENTATION-1 NULL AND THYMUS LEUKEMIA ANTIGEN-POSITIVE MICE()) T)

Thymic selection of natural killer-1(+) natural T cells that express a lpha beta T cell receptors requires a conserved beta 2-microglobulin-a ssociated molecule, presumably CD1d, displayed by CD4(+)8(+) thymocyte s. Here we demonstrate that positive selection of natural T cells occu rs independent of transporters associated with antigen presentation-1 (TAP-1) function. Moreover, natural T cells in TAP-1(0/0) mice are num erically expanded. Several H-2 class Ib molecules function in a TAP-in dependent manner, suggesting that if expressed in TAP-1(0/0) thymocyte s, they could play a role in natural T cell development. Of these clas s Ib molecules, H-2TL is expressed by TAP-1(0/0) thymocytes. Moreover, we find that thymi of TL(+) mice congenic or transgenic for H-2T18 al so have a numerically expanded natural T cell repertoire compared with TL(-) mice. This expansion, as in TAP-1(0/0) thymi, is evident in eac h of the limited T cell receptor V beta chains expressed by natural T cells, suggesting that TL and CD1d impact similar repertoires. Thus TL , in addition to CD1d, plays a role in natural T cell development.