Evaluation of TCR Vβ subfamily T cell expansion in NOD/SCID mice transplanted with human cord blood hematopoietic stem cells

Abstract

Examination of the T cell receptor (TCR) gene repertoire is important in the analysis of the immune status of models, because clonal expansion of T cells permits the identification of specific antigen responses of T cells. Little is known about T-cell immunity in the humanized NOD/SCID mouse model. TCR Vβ repertoire usage and clonality were analyzed to investigate the distribution and clonal expansion of TCR Vβ subfamily T cells in NOD/SCID mice transplanted with human cord blood (CB) hematopoietic stem cells. The NOD/SCID mice were sublethally irradiated (60Co, 300cGy) to eliminate residual innate immunity in the host. The experimental mice were transplanted intravenously with CB CD34+ cells sorted by MACS. After 6 weeks, RNA was obtained from peripheral blood, bone marrow and thymus of the study animals. The gene expression and clonality of the TCR Vβ repertoire were determined by RT-PCR and GeneScan techniques. A restricted range of TCR Vβ usage was exhibited in the bone marrow of mice, which included TCR Vβ 1, 2, 9, 13 and 19. Further, oligoclonal expression of some TCR Vβ subfamilies (Vβ9, 13, 19) was identified by GeneScan technique. To investigate the reason for oligoclonal expansion of the TCR Vβ subfamily T cells from CB 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 frozen and thawed, and used as tissue-antigen. CB mononuclear cells were separately cultured with the component from those murine cells for 15–20 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. Interestingly, a similar clonal expansion of the TCR Vβ11 subfamily was found in T cells cultured with peripheral blood, bone marrow and spleen respectively. The TCR Vβ subfamily T cells could be reconstituted in humanized NOD/SCID mouse transplanted with CD34+ cells from CB. The restricted expression and clonal expansion of some CB T cell clones may be induced by tissue-antigens of NOD/SCID mice.