Expansion of CD62L^hi antigen-experienced memory T cells after low-dose T-cell transfer. (A) B6 wt (CD45.2) recipient mice received 10 naive CD44^lo CD45.1⁺ OT-I T cells and were subsequently infected with 5 × 10³L.m.-Ova. Eight months later, CD45.1⁺ OT-I T cells were identified from living lymphocytes as CD44^hi CD62L^hi and CD62L^lo memory T-cell subsets (B, before cell sorting). Subset cells were FACS purified (B, after cell sorting) and transferred into L.m.-Ova-infected (5 × 10³) B6 wt (CD45.2) recipient mice, respectively. (C) Expansion and differentiation of the transferred memory T-cell subsets were analyzed 12 days later. The frequencies of re-expanded CD45.1 OT-I memory subset T cells in the spleen after transfer of the indicated cell numbers are demonstrated, and representative differentiation patterns of expanded CD45.1⁺ T cells (CD127 and CD62L staining) are shown (n.d., not detectable).