PDCD1 and systemic lupus erythematosus: Through the analysis of T cell DEGs GSVA enrichment scores, we compared the expression levels of immune checkpoint genes (PD-L1, PDCD1, and CTLA-4)47, 48 and T cell exhaustion markers (TIM3, LAG3, HAVCR2, and TIGIT)49 with the differential gene expression patterns of SLE, AD, and PS in the TCGA-SKCM dataset.