CTLA4 and lung cancer: Note that several exhaustion-related genes can serve as markers for separating both subtypes in CD4 and CD8, such as TIGIT and CTLA4. For the CD8+ T cell subtypes, we compared the candidate marker genes identified in our DE analysis to the exhausted CD8+ T cells marker genes reported in a previous single-cell RNA-seq from infiltrating T cells of lung cancer [15].