@ARTICLE{10.3389/fimmu.2019.00299, AUTHOR={Hou, Xianliang and Zeng, Ping and Zhang, Xujun and Chen, Jianing and Liang, Yan and Yang, Jiezuan and Yang, Yida and Liu, Xiangdong and Diao, Hongyan}, TITLE={Shorter TCR β-Chains Are Highly Enriched During Thymic Selection and Antigen-Driven Selection}, JOURNAL={Frontiers in Immunology}, VOLUME={10}, YEAR={2019}, URL={https://www.frontiersin.org/articles/10.3389/fimmu.2019.00299}, DOI={10.3389/fimmu.2019.00299}, ISSN={1664-3224}, ABSTRACT={The adaptive immune system uses several strategies to generate a repertoire of T cell receptors (TCR) with sufficient diversity to recognize the universe of potential pathogens. However, it remains unclear how differences in the T cell receptor (TCR) contribute to heterogeneity in T cell state. In this study, we used polychromatic flow cytometry to isolate highly pure CD4+/CD8+ naive and memory T cells, and applied deep sequencing to characterize corresponding TCR β-chain (TCRβ) complementary-determining region 3 (CDR3) repertoires. We find that shorter TCRβ CDR3s with fewer insertions were highly enriched during thymic selection. Antigen-experienced T cells (memory T cells) harbor shorter CDR3s vs. naive T cells. Moreover, the public TCRβ CDR3 clonotypes within cell subsets or interindividual tend to have shorter CDR3 length and a significantly larger size compared with “private” clonotypes. Taken together, shorter CDR3s highly enriched during thymic selection and antigen-driven selection, and further enriched in public T-cell responses. These results indicated that it may be evolutionary pressures drive short CDR3s to recognize most of antigen in nature.} }