CD28 and neoplasm: Considering the role for microenvironmental supplementation in tumour xenograft success, we next examined the relationship between the expression levels of the different stem/progenitor marker genes and a set of immune microenvironment-related genes, including a number of T- (CD2, CD5, CD7, CD4, CD8A), B-cell markers (CD19, MS4A1, CD79A, CD79B), as well as a number of immune checkpoint pathway genes (CD28, CD80, CD86, CD274 (PD-L1), PDCD1LG2 (PD-L2), PDCD1 (PD1), ICOSLG, ICOS, CD274 and LAG3) (Supp.