PDCD1 and hematopoietic and lymphoid cell neoplasm: By examining immune checkpoints such as PD-1/PD-L1, CTLA-4/CD86, and CD200R/CD200 in different blood lymphocyte subpopulations, we aim to extract valuable insights that may improve not only our understanding of these diseases but also contribute to improving treatment conditions and the occurrence of subsequent complications and the development of hematological cancers.