TM immunolocalization in wild-type (Wt) and TM^−/− chimeric (Ch) lung. PLP-fixed cryosections of mouse lung were stained with an anti-TM rat MoAb and counterstained with hematoxylin. TM is localized to the intimal surface of wild-type mice (a) and some TM^−/− chimeric vessels (b). TM mosaicism is shown in cross sections through blood vessels containing patchy TM staining (c); arrows indicate endothelial nuclei confirming the presence of an intact intima. Also observed are blood vessels completely negative for TM localization (d); arrow indicates adjacent blood vessel immunoreactive with anti-TM antibodies. Original magnification × 630.