Longitudinal analysis reveals age-related changes in the T cell receptor repertoire of human T cell subsets

A diverse T cell receptor (TCR) repertoire is essential for protection against a variety of pathogens, and TCR repertoire size is believed to decline with age. However, the precise size of human TCR repertoires, in both total and subsets of T cells, as well as their changes with age, are not fully characterized. We conducted a longitudinal analysis of the human blood TCRα and TCRβ repertoire of CD4(+) and CD8(+) T cell subsets using a unique molecular identifier–based (UMI-based) RNA-seq method. Thorough analysis of 1.9 × 10(8) T cells yielded the lower estimate of TCR repertoire richness in an adult at 3.8 × 10(8). Alterations of the TCR repertoire with age were observed in all 4 subsets of T cells. The greatest reduction was observed in naive CD8(+) T cells, while the greatest clonal expansion was in memory CD8(+) T cells, and the highest increased retention of TCR sequences was in memory CD8(+) T cells. Our results demonstrated that age-related TCR repertoire attrition is subset specific and more profound for CD8(+) than CD4(+) T cells, suggesting that aging has a more profound effect on cytotoxic as opposed to helper T cell functions. This may explain the increased susceptibility of older adults to novel infections.