In vivo tumor-derived CCL5 chemotactic activity. (A) Tumors from nude mice xenografted with DLBCL cell lines were stained for murine macrophages (F4/80; left panels). Scale bar, 50 µm. A quantitative analysis (mean ± standard deviation [SD]) is shown for a group of 5 mice (right panel). ***P < .001 (B) Flow cytometry analysis of myeloid cells recovered from OCI-Ly18 xenograft tumors (left panel). A quantitative analysis (mean ± SD) for the percentage of infiltrating CD11b⁺/F4/80⁺ macrophages is shown for a group of 10 mice grafted with the indicated tumors (middle panel). Mice were treated systemically with metCCL5 or control phosphate buffered saline (PBS); tumor volume during treatment (arrows show treatment timepoints) is also shown (right panel). ***P < .001. (C) Bone marrow cells from humanized NOG mice were stained for human CD45 (huCD45) and human CD14 (huCD14; upper left panel). The rectangle denotes the presence of human monocytes. Humanized NOG mouse xenografts of the indicated DLBCL cell lines were stained for human macrophages (CD68; upper right panels). Scale bar, 20 µm. A quantitative analysis (mean ± standard deviation) is shown for a group of 3 mice (lower right panel). fluo., fluorescence.