Gating strategy and frequency of the naive and central memory phenotypes (defined as CD28+ CCR7+) in the CD3+CD8+ T cell population. A, CD28+CCR7+ frequencies at 7 wk PC in PBMC and at 12 wk PC in axillary LNMC. B, Gating strategy for characterizing expression of CD28 and CCR7 molecules at 7 wk PC in CD3+CD8+ T cells; the values shown in A for 7 wk PC correspond to the CCR7+CD28+ cell population that is highlighted by an asterisk in the bottom row of B. P, Protected; U, unprotected; FSC, forward scatter; SSC, side scatter.