The Feature of δRec-ψJα sjTRECs Level and Frequency of 23 TCR Vβ-Dβ1 sjTRECs in Mononuclear Cells, CD4+ and CD8+ T Cells from Cord Blood and Peripheral Blood of Normal Individuals.

Thymic recent output function is characterized its importance of thymus to T-cell diversity in the periphery of both children and adults. The generation of TCR diversity occurs in the thymus through recombination of gene segments encoding the variable parts of the TCR α and β chains. During these processes, by-products of the rearrangements are generated in the form of signal joint T-cell receptor excision circles (sjTRECs), which is considered as a very valuable tool to estimate thymic function. Quantitative of δRec-ψJα sjTRECs can direct evaluate the recent thymic output function, but it is unable to analyze the particular thymic output function of different TCR Vβ subfamily naive T cells. The complexity of TCR Vβ repertoire is an important factor for immune reconstitution, quantitative analysis of series TCR Vβ-Dβ sjTRECs could be used to evaluate the levels of different Vβ subfamily naive T cells.

In the present study, quantitative analysis of δRec-ψJα sjTRECs was performed in mononuclear cells, CD3+, CD4+ and CD8+T cells from peripheral blood of normal individuals and cord blood by real-time PCR(TaqMan). And the analysis of 23 TCR Vβ-Dβ1 sjTRECs was performed by semi-nested PCR. Different amounts of DNA (corresponding to 2*10⁵, 5*10⁴, 1*10⁴ and 1*10³ cells respectively) from all samples were amplified to estimate the frequency of TCR Vβ-Dβ sjTRECs.

The mean value of δRec-ψJα sjTRECs was detected in 4.10±3.65/1000 PBMCs, 6.37±5.28/1000 CD3+cells, 3.28±1.24/1000 CD4+cells, 4.67±3.63/1000 CD8+cells from normal individuals (n=14) and 35.59±47.56/1000 CBMC, 71.48±86.42/1000 CD3+cells, 41.02±32.9/1000 CD4+ cells, 52.05±52.32/1000 CD8+cells from cord blood (n=9) (p=0.0208, p=0.0096, p=0.0003, p=0.0026, respectively).

A part of Vβ subfamily sjTRECs could be detected in all samples from cord blood (Vβ2, 3, 4, 5, 10, 13, 14, 15, 19 and 22) and peripheral blood (Vβ10, 13 and 14) at 5*10⁴ cells level, some of Vβ subfamily sjTRECs could be detected in 1*10³ cells level. The frequencies of 23 Vβ-Dβ1 sjTRECs were different at the same cellular concentration. The number of detectable Vβ subfamily sjTRECs was 22.00±0.94/2×10⁵, 18.8±1.87/5×10⁴, 10.40±2.99/1×10⁴ and 0.78±1.39/1×10³ CBMCs, as compared with 18.70±2.45/2×10⁵ (p=0.002), 13.7±2.67/5×10⁴ (p<0.001), 5.5±2.07/1×10⁴ (p=0.001) and 0.50±0.71/1×10³ (p=0.739) in PBMCs from normal individuals. Similar results were found in CD4⁺ and CD8⁺ T cells which were sorted from both CBMCs and PBMCs, the number of detectable Vβ subfamily sjTRECs was 13.90±2.38/1×10⁴ CD4+cells, 11.5±1.96/1×10⁴CD8+cells from cord blood and 5.6±2.68/1×10⁴ CD4+cells (p<0.001) and 8.2±2.57/1×10⁴CD8+cells (p>0.005) from normal individuals. The results indicate that the number of detectable sjTRECs of Vβ subfamilies and the frequencies of most Vβ-Dβ1 sjTRECs in normal PBMCs, CD4⁺ and CD8⁺T cells were obviously lower than those in cord blood.

In conclusions, the results provide the base data of naïve T cells levels and thymic recent output function in cord blood and peripheral blood of normail individuals in chinese.