Immunohistochemical detection of human CD66b expression in CGM6-transgenic mice. Cryosections from various organs were incubated with a polyclonal rabbit anti-NCA antiserum followed by a peroxidase-coupled, antirabbit IgG and stained for peroxidase activity (brown). Counterstaining of nuclei was with hematoxylin (blue). (A) The spleen from a CGM6-transgenic mouse shows staining of granulocytes (see inset) mainly in the red pulp areas. (B) The spleen from a nontransgenic sibling mouse is negative. The lung (C) and a blood smear (D) of a CGM6-transgenic mouse also show granulocyte staining (Al = alveolus). Black arrowheads indicate stained granulocytes (see inset in D) and white arrowheads are nonstaining lymphocytes. (E) Section through the lung (Lu) and liver (Li) of a day 17.5 CGM6-transgenic mouse fetus. Black arrowheads show granulocyte staining concentrated along the edge of a liver lobe and lining a blood vessel (BV). Open arrows show ribs containing stained granulocytes in the bone marrow. (F) Higher magnification showing stained granulocytes in the rib bone marrow (BM). Bars = 5 μm (D: inset), 50 μm (A: inset, C and D), 100 μm (A, B, and F), and 500 μm (E).