[Defective generation of NK1.1+ T cells in aly/aly mice associated with thymic architecture].

It has been reported that positive selection of natural killer antigen 1.1+ (NK1.1+) T cell antigen receptor (TCR) alpha beta+ thymocytes recently identified among CD4+8- and CD4-8- subpopulations is attributable to major histocompatibility complex (MHC) class Ib ligands expressed on bone marrow (BM) derived components in the thymus. This selection pattern is quite different from NK1.1-T cells of main stream. In the present study, we investigated generation of NK1.1+ TCR alpha beta+ cells in the thymus of aly/aly mouse which lacks lymph nodes and Peyer's patches and shows abnormalities of thymic and splenic structure. We found that the proportion of the NK1.1+ TCR alpha beta+ thymocytes was extremely low in these mice as compared with aly/aly+ and normal C57BL/6 mice. Thymic reconstitution by BM cells from aly/aly+ mice which possess a normal population of NK1.1+ TCR alpha beta+ thymocytes did not restore the NK1.1+ TCR alpha beta+ cell population in the thymus of lethally irradiated aly/aly mouse. When deoxy-guanosine (dGuo)-treated fetal thymi from (B6 x B10.G) F1 mice were transplanted to aly/aly mice which had been thymectomized and reconstituted with BM cells of aly/aly mice, normal proportions of the NK1.1+ TCR alpha beta+ thymocytes were observed in the thymus grafts. Furthermore it was demonstrated that NK1.1+ T cells in aly/aly mice were unable to produce efficiently IL-4 upon in vivo stimulation with anti-CD3. These findings demonstrate that the development of NK1.1+ TCR alpha beta+ cells is accomplished under the influence of not only BM derived components but also in intact microenvironment of lymphoid tissues.