KLRC1 and atrial fibrillation: To further dissect T cell heterogeneity in AF, we performed unbiased clustering of T cells, identifying three distinct subsets: (1) Th1-polarized memory T cells (Th1-MT, marked by IL7R, CD2, THEMIS, IFNG-AS1, BCL11B), (2) cardiac lipid-adapted memory T cells (CLM-T, characterized by NNMT, ABCA6, TCF7L2, LRP1, EGFR), and (3) NK-like cytotoxic T cells (NK-CTL, expressing KLRF1, GNLY, KLRC1, NCR1, SYK) (Figures 8A–D).