CD4 and infection: In samples from chickens and turkeys that received vaccination, vaccination and infection, or only infection divergences in the numbers of B cells, CD3ε+CD4+CD8α− and CD3ε+CD4−CD8α+ cells were observed by FCM: in the early stage of infection (4 DPI) the main changes were observed in vaccinated and infected turkeys (group VIT) when all lymphocyte subpopulations decreased in the caecum but increased in the blood.