Alefacept treatment depleted CD4 + and CD8 + central memory T cells ( Tcm ) and effector memory T cells ( Tem ) ( P < 0.01 ) , preserved Tregs , increased the ratios of Treg to Tem and Tcm ( P < 0.01 ) , and increased the percentage of PD-1 + CD4 + Tem and Tcm ( P < 0.01 ) .