Bleeding in irritant contact dermatitis in thrombocytopenic mice. (A) Thrombocytopenia was achieved by administration of a rat antimouse GPIbα antibody. Platelet counts were determined at indicated time points and displayed in relation to the baseline level (100%). Platelet depletion occurred within minutes (first data point = 0.1 hours) and platelet counts remained < 2.5% for or over 24 hours). Control IgG antibody injection did not alter platelet counts. (B) WT mice were subjected to irritant contact dermatitis (ICD) in the presence and absence of platelets. Erythema and edema were seen in both groups, while massive bleeding into the skin at the inflammatory ring was seen only in thrombocytopenic mice (right). Mice were killed 4 hours after stimulation. Bar = 5 mm. (C) Hemoglobin content in biopsies of the ICD-treated skin. Control skin has barely detectable levels of hemoglobin that were significantly elevated in the inflamed skin of thrombocytopenic mice (P < .001; n = 5). Error bars represent SEM. (D) Skin sections stained with hematoxylin and eosin show massive RBC accumulation (arrows) in the tissue only of ICD-challenged thrombocytopenic animals. Bar = 40 μm.