PDCD1 and neoplasm: A number of research groups have demonstrated the presence of spatiotemporal correlation between effector CD8+ T-cells and tumor-associated macrophages, moreover, expression levels of M2 markers (CD163+, CD206+, etc.)closely correlated with T-cell exhaustion—condition, characterized by dysfunction of effector cells and marked by the upregulation of inhibitory receptors (such as programmed cell death-1 (PD-1), T cell immunoglobulin and mucin domain-3 protein (TIM-3), etc.)[66,67].