Figure 2.

Effect of sP-sel on fibrin distribution at the Shwartzman reaction lesion site. (A) Micrographs showing fibrin deposition (F) in paraffin section from the Shwartzman lesion site. Tissue sections from WT mice treated with IgG1 or P-sel-Ig were immunostained with antibodies to fibrinogen. Note the presence of hemorrhage (H) in the section from the IgG1-treated animals, and a diffuse staining for fibrin inside and outside the vessel. A strong fibrin staining (F) is found on the luminal face of the vessel wall in the P-sel-Ig-treated mice, without detectable fibrin deposition in the surrounding tissue. White arrowheads point to the vessel wall. Bar = 40 μm. (B) Evaluation of fibrin localization relative to the vessel wall of all blood vessels observed in paraffin sections at the lesion site. “Leakage” annotates blood vessels that presented fibrin staining outside the vessel wall. Blood vessels that had fibrin staining only at the luminal face of the vessel wall were classified as “luminal ring.” The frequency of vessels showing leakage was 3-fold higher in WT mice treated with IgG1 than with P-sel-Ig (*, P < 0.0001). In contrast, the luminal ring was more common in the P-sel-Ig-treated group than in the IgG1 controls (†, P < 0.005). The counting was performed on samples from 7 mice injected with P-sel-Ig and from 10 mice injected with control IgG1. A minimum of 100 vessels were observed per lesion site.