CD4 and neoplasm: MDV infection progresses in 3 major phases: (i) an early cytolytic infection corresponding to the entry of the virus through the respiratory tract and its transport to the lymphoid organs where it infects B-cells and activated T-lymphocytes; (ii) a latent phase (between 7 to 10 days post-infection (pi)) in CD4 + T lymphocytes, which is characterized by the integration of the viral genome into the genome of the host cells; (iii) the tumor phase occurring in CD4 + T lymphocytes leading to malignant lymphoma formation and the death of animals from the 3rd week of infection [1, 2].