CCR5 and neoplasm: When examined for immune cell infiltrates, 0.4-0.5 cm diameter tumors harvested from 3 MMTV-PyMT.CCR5+/+ and 3 MMTV-PyMT.CCR5−/− mice 18 days post-tumor onset exhibited no significant differences in CD45+ leukocyte infiltrates; MMTV-PyMT.CCR5+/+ derived tumors: CD45 staining index (signal intensity per field normalized over background) = 181 ± SEM 11 per field (20× magnification), 3 fields per thin section.