Animals reconstituted with mixtures of wild-type and CD18^−/− hematopoietic cells 6 months previously were labeled with BrdU for 24 hours. Expression of Gr-1 and incorporation of BrdU were determined by flow cytometry. The percentages of wild-type and CD18^−/− neutrophils (Gr-1⁺) that incorporated BrdU are shown. The percentages of Gr-1⁺ cells that were CD18-deficient were 85%, 83%, and 79% in animals 1, 2, and 3, respectively. A separate experiment, again with 3 mice, confirmed no differences in BrdU-labeling indices between WT and CD18-deficient neutrophils in the marrow.