F/P-positive CEL mice have MC infiltration in relevant nonhematopoietic organs. (A) Levels of mast cells in the small intestine. Levels of intestinal mast cells in F/P-positive CEL and CD2-IL-5Tg/mock vector–transduced recipient mice were assessed after development of disease (at 4-5 weeks after transplantation) by morphometric analysis of chloroacetate esterase (CAE)–stained cells. Results are shown as mean (± SEM) from 4 mice per group of one representative experiment (n = 3 experiments). *P < .001. (B) Representative small intestine section from F/P-introduced F/P-positive CEL and control mice with CAE staining (original magnification, ×125), indicating a preferential intraepithelial localization of MCs in F/P-positive CEL mice. Images taken with Leica DMI6000B microscope (Wetzlar, Germany) 10× PH1 acquired with color Leica camera and Open Lab software version 5.50 (Improvision, Waltham, MA). (C) Levels of cutaneous mast cells in F/P-induced, F/P-positive CEL and donor-matched control mice were assessed as in panel A. Results are shown as means (± SEM) from 4 mice per group of one representative experiment. Three independent experiments were conducted with similar results; *P < .05.