PDCD1 and hepatocellular carcinoma: Less common immunosuppressive cell types in human HCC consist of B cell population expressing PD-1, Th17 cells, CD4+ T cells expressing CCR4 and CCR6, CD14+ DCs expressing CTLA-4 and PD-1, tumor-associated neutrophils, tumor-associated fibroblasts, and type-II T helper cells (Th2) (74–77).