Conventionally, dual positive cells (CD27+CD45RA+) are considered naïve; expression of CD27 alone (CD27+CD45RA−) is described as a central memory population; the absence of CD27 allows cells to migrate to the site of infection, those that express neither marker (CD27−CD45RA−) are described as effector memory T cells, while those that re-express CD45RA (CD27−CD45RA+) are terminally differentiated memory cells. Here, CD27 is linked to infection.