CD8 T cells play a key role in elimination of intracellular pathogens. Here, we have carried out a detailed phenotypic and functional analysis of swine blood CD8β T cells, after vaccination with a live attenuated PRV vaccine. Based on the expression of six surface molecules (CD11a, CD27, CD45RA, CD95, CCR7 and SLA-DR), up to eight subsets can be identified within the circulating compartment of CD8β T cells of adult pigs
six of which correlate phenotypically with naïve, stem cell memory, central memory, transitional memory, effector memory, and terminal effector subsets described in humans. The remaining two subsets appear to correspond to intermediate stages between naïve and central memory cells, and between transitional memory and effector memory or terminal effector cells, respectively. Although CD45RA has been proposed as a marker to distinguish between porcine naïve and central memory CD8β T cells, we found that a substantial proportion of naïve T cells, which varies among animals, lack this marker and that the combination of CD95 and CD11a allows a more accurate discrimination of these subsets among CD27