A unique CD4 T-cell subpopulation emerges during SS. (A) UMAP plot demonstrating 2 clusters of CD4 T cells. Cells are color coded by clusters. (B) Bar plots of the proportion of CD4 T cells in cluster 7 from patients with MF and SS. (C) Bar plots of the proportion of CD4 T cells in cluster 1 from patients with MF and SS. (D) Bar plots enumerating monoclonality for CD4 (left) and CD8 (right) in MF and SS. (E) Box plots comparing enrichment scores for the indicated phenotype among cluster 1 and cluster 7 cells. Center line, median; box limits, upper and lower quartiles. (F) Violin plots of selected genes for multiple immune cell types. (G) Single-cell trajectory plot showing lineage relationships among cluster 1 and 7 cells from patients with MF and SS using the Monocle algorithm. (H) Heat map depicting temporal marker expression intensity for significantly branch-dependent genes (Branch Expression Analysis Modeling test; false discovery rate of <1 × 10⁻¹⁰) for the transition identified in panel G. ∗P < .05 by 2-tailed t test. ns, nonsignificant.