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.