Ly6C supports preferential homing of central memory CD8+ T cells into lymph nodes.

Ly6C is a murine cell-surface antigen expressed by plasma cells, subsets of myeloid cells and many T cells, including memory T cells. We previously documented that Ly6C crosslinking induces LFA-1 clustering on naïve CD8(+) T cells. Here, we show that in vitro and in vivo differentiation of naïve CD8(+) T cells into central (Tcm) but not effector (Tem) memory T cells enhances Ly6C expression, and its crosslinking induces strong LFA-1 clustering on Tcm. Blocking Ly6C function inhibits in vivo Tcm homing to LNs as efficiently as blocking L-selectin but it does not potentiate the inhibition provided by blocking either L-selectin or LFA-1 function. Thus, Ly6C, L-selectin and LFA-1 all appear to be part of a common homing pathway. In vitro, Ly6C crosslinking enhances Tcm adherence to ICAM-1 in the presence of CCL21. In summary, Tcm homing involves Ly6C, in addition to L-selectin and LFA-1, and appears to potentiate firm adhesion of Tcm to ICAM-1 in synergy with a chemokine. We propose that Ly6C augments Tcm compartmentalization into LNs during their homing.