The immune cell composition is variable in different tumors, but generally includes quantitatively and functionally different populations of CD4+ T cells, CD8+ T cells, natural killer (NK) cells, dendritic cells (DCs), tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), myeloid-derived suppressor cells (MDSCs), and B cells (Figure 1). Here, CD8A is linked to neoplasm.