Homeostatic proliferation of memory CD8 T cells. (A) Histograms show the percentage of VSV-N–specific memory CD8 T cells that have incorporated BrdU. (B) Spleen cells from normal, CD45.1⁺, VSV-infected mice were enriched for CD8 T cells, labeled with CFSE, and transferred to various CD45.2⁺ hosts. Two months after transfer, lymphocytes from SP, LG, and BM were analyzed for CFSE intensity. Top panels show CFSE dilution in CD45.1⁺ CD44^hi CD8⁺ T cells (memory-phenotype) in various tissues. Bottom row depicts CFSE dilution in splenic N-tetramer⁺ cells.