Successful single-cell transfer of CD62L^hi antigen-experienced CD8⁺ memory T cells. (A) Adoptive transfer protocol from H2-K^b/SIINFEKL-Streptamer–enriched polyclonal (not TCR transgenic) memory T cells. (B) MHC-Streptamer–positive CD62L^hi CD8⁺ memory T cells were identified in spleens of L.m.-Ova-immune CD45.1 wt mice (B, before cell sorting) and FACS purified (purities in B, after cell sorting). Streptamer reagents were removed after addition of d-biotin, and cells were immediately transferred into RAG^−/− mice. Recipient mice were MVA vaccinated and L.m.-Ova challenged in analogy to Figure 1. (C) Bacterial counts in spleen and liver of mice with the indicated transferred T-cell numbers are shown (n.d., not detectable). Negative control mice had undetectable CD45.1-OT-I T cells after single-cell transfer (no cells).