Immunophenotypic characterization of BM-derived T cells. BM-, PB-, and LN-derived mononuclear cells were obtained from healthy SIV-uninfected SMs and RMs. (A) Flow cytometric analysis was used to assess the percentage of BM-, PB-, and LN-derived mononuclear cells that express CD3, CD4, CD8, CD16, and CD20 in SMs and RMs. The CD4/CD8 ratio is also shown. Numbers indicate mean plus or minus SD. (B) Staining of CD4⁺ and CD8⁺ T cells in BM, PB, and LN of a representative SM and RM. BM-derived T cells include an increased proportion of CD8⁺ T cells with decreased CD4/CD8 ratio compared with the other sites.