CD4 and cancer: We found that the HHLA2 expression was significantly linked with lots of infiltrating immune cells: B cells in 20 types of cancer, CD4+ T cells in 12 types of cancer, CD8+ T cells in 13 types of cancer, macrophages in 13 types of cancer, neutrophils in 12 types of cancer, and DCs in 15 types of cancer (Figure 9).