3.8 UVB enhances Treg clonal expansion in human peripheral
blood
To further validate Treg expansion induced by UVB, we integrated
scRNA-seq and TCR VDJ sequencing data obtained from peripheral blood
samples from the above two psoriasis patients, focusing on
CD4+ T cells. We identified four distinct populations
— naive T cells, T effector cells, T memory cells, and Tregs (Figure
6E, left) — of which a more condensed Treg population was observed
after UVB treatment, suggesting clonal expansion (Figure 6E, right). To
quantify this, we categorized clonotypes based on the number of cells
expressing each TCR sequence: single (0 < X ≤1), small (1
< X ≤ 5), and medium (5 < X ≤ 20). The proportion of
small-to-medium clonal expansions increased within the Treg cluster
post-UVB treatment (from 5.26% to 11.42%) (Figure 6F). Additionally,
we calculated expansion indices using the Shannon entropy-based STARTRAC
method. In both patients, a higher expansion index was noted in post-UVB
Tregs compared to pre-UVB Tregs (Figure 6G). In conclusion, our TCR
sequencing analysis demonstrates that UVB induces clonal expansion in
human peripheral Tregs.