In NHPs, BM contains higher levels of proliferating CD4⁺ and CD8⁺ T cells than PB and LN. The fraction of CD4⁺ and CD8⁺ T cells expressing the proliferation marker Ki-67 was assessed in BM, PB, and LN of 10 SIV-uninfected SMs and RMs. (A) Staining of CD4⁺Ki-67⁺ T cells in the different anatomic sites of a representative SM (left panel) and RM (right panel). (B) Percentage of CD4⁺ and CD8⁺ T cells that express Ki-67 in BM, PB, and LN in 10 SIV-uninfected SMs and RMs. P values are shown when significant differences between groups are present. (C) Assessment of in vitro T-cell proliferation using CFSE staining in PB- and BM-derived CD3⁺ T lymphocytes in a representative SM after 5 days in vitro stimulation with 1 μg/mL ConA.