PDCD1 and neoplasm: Transcriptional profiles revealed antigen-related genes in ILTCK progenitors, suggesting autoantigen-driven selection, with Fcer1g emerging as a lineage-defining marker for ILTCK, already upregulated in thymic progenitors and expressed in differentiated and activated tumor-infiltrating ab ILTCKs, but not in CD8+PD1+ T cells (Figure 4) [212,218].