Differentiation of central memory CD8 T cells is independent of CD62L-mediated trafficking to lymph nodes.

CD62L (L-selectin) is a key regulator of T cell trafficking, and its surface expression on activated T cells is modulated to control T cell access to lymph nodes after acute infections. In memory T cells, CD62L is the most frequently used marker to define central memory T cells, a population that provides enhanced protection against most, but not all, pathogens. Early access of CD62L(pos) effector T cells to lymph nodes has been proposed to result in preferential central memory T cell differentiation, but direct proof for the involvement of lymph node homing in memory T cell differentiation is lacking. In this study, we show that central memory lineage commitment in CD8 T cells is unaltered by enhanced entry into lymph nodes as a result of constitutive CD62L expression, and that equal numbers of effector and central memory CD8 T cells develop in the absence of CD62L-mediated lymph node trafficking. Our results suggest that CD62L is not a deterministic marker of central memory T cell differentiation, thus providing new insight into the process of memory CD8 T cell generation.