Therefore, the aim of this publication was to evaluate three immunological checkpoints of their ligands: PD-1 (CD279)/PD-L1 (CD274), CTLA-4 (CD152)/CD86, and CD200R/CD200 in the course of immunodeficiencies, on the example of CLL and CVID. The gene discussed is PDCD1; the disease is B-cell chronic lymphocytic leukemia.