The Feature of TCR Vβ Subfamily T Cells Expansion in NOD/SCID Mice Transplanted with Human Cord Blood Hematopoietic Stem Cell.

Reconstitute of functional human lymphocytes in some mouse strains has been intensely explored because this approach could provide a valuable means of assessing human immunity or of preclinical testing of vaccines, pathogens, and new therapeuticstrategies. The NOD/SCID mouse strain was found to be an efficient recipient for the reconstitution of human hematopoietic cells. In these xenogenic transplantation models, growth of human lymphocytes has been demonstrated in bone marrow, peripheral blood and spleen of the mice after i.v. inoculation. These mouse models showed the multilineage differentiation of human hematopoietic cells to varying degrees. Moreover, the engraftment of human hematopoietic cells is highly variable. Complete multilineage differentiation, especially T cells, has not been achieved using this strain. Examination of T cell receptor (TCR) gene repertoire is important to analysis the immune status of models, because clonal expansion of T cells permit the identification of specific antigen response of T cells. Little is known about the feature of T-cell immunity in the humanized NOD/SCID mouse model.In order to investigate the distribution and clonal expansion of TCR Vβsubfamily T cells in NOD/SCID mice transplanted with human cord blood hematopoietic stem cell. TCR Vβ repertoire usage and clonality were analyzed. The NOD/SCID mice were sublethally irradiated (⁶⁰Co, 300cGy) to eliminate residual innate immunity in the host. The experimental mice were transplanted intravenously with cord blood CD34⁺ cells sorted by MACS. After 6 weeks, RNA was obtained from peripheral blood, bone marrow, thymus of model. The gene expression and clonality of TCR Vβ repertoire were detected by RT-PCR and GeneScan technique. A certain range of TCR Vβ usage was exhibited in the bone marrow of mice, which included TCR Vβ1, 2, 9, 13, 19. Further, oligoclonal expression of some TCR Vβ subfamilies (Vβ9, 13, 19) were identified by GeneScan technique. To investigate the reason involving oligoclonal expansion of TCR Vβ subfamily T cells from cord blood in mouse models, the T-cell culture with tissue-antigen of NOD/SCID mouse was performed in vitro. The cells from peripheral blood mononuclear cells and bone marrow, spleen, thymus in NOD/SCID mice were wiped off by freeze thawing and served as tissue-antigen. Cord blood mononuclear cells were separately cultured with the component from those murine cells for 15 to 20 days. Oligoclonal expression or oligoclonal trend of some TCR Vβ subfamilies (Vβ10, 11 and Vβ2, 15, 16, 19) was detected in T cells after stimulation with tissue-antigen of NOD/SCID mouse. Interesting, the similar clonal expansion of TCR Vβ11 subfamily was found in T cells cultured with peripheral blood, bone marrow and spleen respectively. The results indicate that the TCR Vβ subfamily T cells could be reconstituted in humanized NOD/SCID mouse transplanted with CD34⁺cells from cord blood. The restricted expression and clonal expansion of some CB T cell clones might be induced by tissue-antigens of NOD/SCID mice.