Immunohistologic staining for Kupffer cells in radiation bone marrow chimeras. B6.CD45.2 recipient mice were irradiated (10 Gy) and reconstituted with B6.CD45.1 bone marrow. Frozen tissue sections were stained for macrophages (F4/80), CD45.1⁺ BM-derived cells, and CD45.2⁺ recipient-derived cells, revealing Kupffer cells derived from donor BM (purple-red), sessile recipient-type KCs (orange-green), BM-derived non-KC leukocytes (blue), and recipient-type non-KC leukocytes (green). (A) Liver tissue sections 4 weeks (left) and 13 weeks (right) after bone marrow transplantation, showing an equal distribution of BM-derived and sessile KCs. Original magnification, ×200. (B) Higher magnification of BM-derived and sessile KCs 4 weeks (left) and 13 weeks (right) after bone marrow transplantation. Original magnification, ×400. (C) Quantitative analysis of the 2 KC subsets revealed that 46% (± 3%) were sessile KCs of recipient origin. Error bars represent SEM.