PDCD1 and myeloid sarcoma: Resident memory CD4+ T cells in human brain have been characterized as having mixed Th17/Th1 features26,29, and cluster 8 also showed relatively high expression of markers of these cells, some of which overlap with markers of pathogenicity, and include CCR5, CXCR6, PD-1(PDCD1), GZMA, ZFP36L2, and ID2. By contrast, cluster 0 does not show relatively high expression of resident markers but does show higher expression of some genes associated with pathogenic cells based on studies of MS patients, including ITGA4 and TNFRSF2528.