TRGV and TRDV repertoire distribution and clonality of T cells from umbilical cord blood

Umbilical cord blood (CB) has been used as a valuable source of hematopoietic stem cells for allogeneic transplantation, specific CTL response and immunotherapy for decades. We previously analyzed the distribution and clonality of T-cell receptor alpha and beta variable region (TRAV) and (TRBV) of the subfamily T cell receptors in T cells from umbilical cord blood. Recent data indicated that γδ+ T cells may play an important role in mediating the graft versus leukemia effect after stem cells transplantation and in anti-cancer response. In order to further characterize the repertoire of CB T-cells, the frequency of αβ+ and γδ+ T cells were examined in CB by FACS. The CDR3 size of 4 TRGV and 8 TRDV subfamily genes were analyzed in mononuclear cells (MCs) from 16 CB samples, using RT-PCR and genescan technique. To determine the expression level of TRGV subfamily genes, we performed quantitative analysis of TRGVI–III subfamilies by real-time PCR. Low percentage of CD3+TCRγδ+ cells was observed in CB. The frequency of expression in TRGVI, TRGVII and TRGVIII in CBMCs was 93.75%, 81.25% and 56.25%, respectively. The mean value of the number of expressed TRDV subfamilies in CBMCs is higher than that from adult peripheral blood (PB) group. The frequently expressed members in CB were TRDV1 (100%), TRDV2 (93.75%), TRDV8 (93.75%) and TRDV3 (81.25%), respectively. The frequencies of TRDV5 and TRDV8 in CBMCs were significantly higher than those from PBMCs. Most of the PCR products of TRGV and TRDV subfamilies from 10 CB samples displayed polyclonal rearrangement pattern, whereas one or two PCR products from 6 CB samples showed oligoclonality or biclonality. In contrast, PCR products from 9 of 10 adult healthy controls contained at least an oligoclonal peak in different TRGV or TRDV subfamilies respectively. The pattern of TRGV subfamily expression level in CBMCs was TRGVI > TRGVIII > TRGVII, and in contrast, TRGVII > TRGVI > TRGVIII was found in PBMCs. In conclusion, our results indicate polyclonal and more diverse TRDV segment usage in CB γδ+ T-cells. The pattern of TRGV expression levels in CB T cells was found to be quite different from the one in PB T cells. These findings are apparently the first report regarding the repression pattern of TRGV repertoire in CB. It also provides a detailed profile of the global TRGV and TRDV repertoire and TRGVI-III expression levels in cord blood T cells in Chinese subjects. The biological significance of the differences observed between CB and PB is at present obscure. However, this study will definitively contribute to understand the cellular immune features better and to exploit more efficiently the therapeutic potentials of CB.