Expansion of natural (NK1⁺) T cells that express αβ T cell receptors in transporters associated with antigen presentation-1 null and thymus leukemia antigen positive mice

Thymic selection of natural killer-1¹ natural cells that express αβ T cell receptors requires a conserved β2-microglobulin-associated molecule, presumably CD1d, displayed by CD4⁺8⁺ thymocytes. Here we demonstrate that positive selection of natural T cells occurs independent of transporters associated with antigen presentation-1 (TAP-1) function. Moreover, natural T cells in TAP-1(0/0) mice are numerically expanded. Several H-2 class Ib molecules function in a TAP-independent manner, suggesting that if expressed in TAP-1(0/0) thymocytes, they could play a role in natural T cell development. Of these class 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 also have a numerically expanded natural T cell repertoire compared with TL⁺ mice. This expansion, as in TAP-1(0/0) thymi, is evident in each of the limited T cell receptor Vβ chains expressed by natural T cells, suggesting tat TL and CD1d impact similar repertoires. Thus TL, in addition to CD1d, plays a role in natural T cell development.