GENERATION OF NK1.1(-CELL ANTIGEN RECEPTOR ALPHA() T)BETA(+) THYMOCYTES ASSOCIATED WITH INTACT THYMIC STRUCTURE/

The development of T cells within the thymus is largely dependent on i ntact corticaI and medullary epithelial cells. However, it has been re ported that positive selection of natural killer antigen 1.1(+) (NK1.1 (+)) T cell antigen receptor (TCR)-alpha/beta(+) thymocytes recently i dentified among CD4(+)8(-) and CD4(-)8(-) subpopulations is attributab le to major histocompatibility complex class Ib ligands expressed on b one marrow (BM)-derived components in the thymus. In the present study , we investigated generation of NK1.1(+) TCR-alpha/beta(+) cells in th e thymus of the aly/aly mouse which lacks lymph nodes and Peyer's patc hes and shows abnormalities of thymic and splenic structure, We found that the proportion of the NK1.1(+) TCR-alpha/beta(+) thymocytes was e xtremely low in these mice as compared with aly/+ and normal C57BL/6 m ice, Thymic reconstitution by BM cells from aly/+ mice that possess a normal population of NK1.1(+) TCR-alpha/beta(+) cell population did no t restore the NK1.1(+) TCR-alpha/beta(+) cell population in the thymus of lethally irradiated aly/aly moose. When deoxyguanosine-treated fet al thymi from (B6 x B10.G)F-1 mice were transplanted to aly/aly mice t hat had been thymectomized and reconstituted with BM cells of aly/aly mice, normal proportions of the NK1.1(+) TCR-alpha/beta(+) thymocytes were present in the thymus grafts, These findings demonstrate that the development of NK1.1(+) TCR-alpha/beta(+) thgmocytes is accomplished under the influence not only of BM-derived components, but also of irr adiation-resistant or deoxyguanosine-resistant components and an intac t microenvironment of the thymus.