The Feature of Distribution and Clonality of TCR Vα and Vβ Repertoire in Cord Blood.

Analysis of T cell receptor (TCR) Vα and Vβ repertoire is one of the sensitive methods to understand the distribution and clonality of T cells from different samples, which is used to identify clonal expansion T cells that response to tumor associated antigens. Cord blood has been used successfully as a source of hematopoietic stem cells for transplantation. Recently, stem cells transplantation was demonstrated more important as immunotherapy against malignance cells. And cord blood T cells are resourceful for production the specific CTL to use in leukemia immunotherapy. But the feature of distribution and clonality of TCR Vα and Vβ subfamily T cells in cord blood is not yet clearly defined. In the present study, the CDR3 of 29 TCR Vα and 24 Vβ subfamily genes were analyzed in T cells from 10 cases of cord blood, which obtained at delivery from full-term healthy pregnancies, using RT-PCR and genescan technique. Peripheral blood of nine cases healthy adult volunteers served as controls. The results showed that 15–19 of 29 Vα and 9–15 of Vβ subfamily T cells could be identified in the most cases, whereas only 2–4 of Vα subfamilies expressed was found in 3 cases. The most frequently expressed Vα subfamilies were Vα 3 and Vα 10 (100%), Vα 4, 5, 6, 8, 12, 15, 17 and Vα 21 (70%), Vα1, 13, 25, and Vα26 (60%), with a lower expression rate found in Vα16, 24 and Vα 28 (10%). Vα 9 and Vα 29 were not detected in both CB and healthy adults. In analysis of TCR Vβ repertoire, Vβ3, 5, 8 and Vβ9 genes could be identified in all samples, Vβ7 and Vβ13 could be found in 90% of samples, whereas Vβ4, 6, 11, 12, 18, 23 and Vβ24 were absent in all samples, which could be detected in normal peripheral blood samples. Genescan analysis showed that all PCR products of TCR Vα and Vβ subfamilies from cord blood displayed a Gaussian distribution of CDR3 lengths (multi-peaks), which are corresponding to polyclonal rearrangement pattern, except for tow cases, which displayed oligoclonal peak in Vα 24 or Vα28 respectively. In contrast, some Vα subfamily products from 8 of 9 cases of healthy adult volunteers contained at least an oligoclonal peak in different Vα subfamilies respectively, however, multi-peaks were found in all PCR products of TCR Vβ from normal peripheral blood. In conclusion, more than 20% of TCR Vα or Vβ subfamily T cells were absent in cord blood. The majority of TCR Vα and Vβ subfamily T cells in cord blood displayed polyclonality. Occasional oligoclonal peaks are identified in some cases.