PDCD1 and hematopoietic and lymphoid cell neoplasm: Some hematological tumor cells can easily cross-talk with normal immune cells in the secondary lymphoid organs (e.g. follicles), where the cancer cells interact with dendritic cells or T-follicular helper and this interactions may also impact immune therapies, such as anti-PD1 immune checkpoint blockade, since PD1 is highly expressed on T- follicular cells (44).