LY-6C IS A MARKER OF MEMORY CD8(+) T-CELLS

This study examined long-term phenotypic and functional effects of TCR ligation in vivo. Flow cytometric analysis of T cells from mice treat ed with anti-CD3 revealed an increase in CD44 expression in both the C D4(+) and CD8(+) populations. The phenotypic changes were a result of TCR engagement, because treatment with staphylococcal enterotoxin B (S EB) resulted in a preferential increase in CD44 expression on the SEB- reactive V beta 8 T cells. In addition, the percentage of cells expres sing Ly-6C increased among the CD8(+) subset after anti-CD3 treatment and in the V beta 8(+) CD8(+) subset after treatment with SEB. Finally , the TCR transgenic (Tg) mouse strain 2C was used to confirm that the phenotypic changes can be induced by exposure to a physiologic ligand (H-2L(d)). Before treatment, nearly all of the Tg(+)CD8(+) cells were CD44(low)/Ly-6C(-). Tg(+) peritoneal exudate T cells isolated from mi ce challenged with P815 cells (H-2L(d)) up-regulated Ly-6C and secrete d higher levels of IFN-gamma on a per Tg(+) CD8(+) T cell basis after treatment. Taken together, these data indicate that in vivo TCR/CD3 en gagement results in phenotypic and functional changes in T cells. Furt hermore, Ly-6C expression correlates with an increase in IFN-gamma pro duction after antigenic stimulation of CD8(+) T cells, suggesting that it is a ''memory'' marker that correlates with Ag-specific functional changes in CD8(+) T cells.