Differential contributions of central and effector memory T cells to recall responses

Although the absolute number of memory CD8⁺ T cells established in the spleen following antigen encounter remains stable for many years, the relative capacity of these cells to mediate recall responses is not known. Here we used a dual adoptive transfer approach to demonstrate a progressive increase in the quality of memory T cell pools in terms of their ability to proliferate and accumulate at effector sites in response to secondary pathogen challenge. This temporal increase in efficacy occurred in CD62L^lo (effector memory) and CD62L^hi (central memory) subpopulations, but was most prominent in the CD62L^hi subpopulation. These data indicate that the contribution of effector memory and central memory T cells to the recall response changes substantially over time.