Immunohistochemical detection of sPLA₂-V in sections of injured vessels with an attached thrombus. (A-D) Carotid artery sections of a mouse subjected to left carotid artery laser injury model. Rabbit anti–mouse sPLA₂-V Ab (A,C) or Masson trichrome for fibrin detection (B,D) was used. (A) sPLA₂-V was present in the injured carotid artery: in endothelial cells (arrow), neutrophils (arrowhead), vascular smooth muscle cells (*), and around fibrin in the lumen. (B) The soft purple staining in the lumen of the injured carotid artery revealed the presence of extensive fibrin deposits. (C) There was no sPLA₂-V in the noninjured carotid artery. (D) Fibrin was not detected in the noninjured artery. (E-G) The presence of sPLA₂-V was also studied in human left atrial tissue sections. (E) sPLA₂-V was absent in the atrial sample of a patient in sinus rhythm. (F-G) sPLA₂-V was detected around the fibrin thrombus and along the endothelial lining in the atrial section corresponding to a patient in atrial fibrillation. The microscope was a Nikon Eclipe 80i (Nikon Instruments Inc) equipped with a DXM1200F digital camera (Nikon). Panels A, B, and E through G were captured with a 40×/0.75 NA objective (Plan Fluor; Nikon). Panels C and D were captured with a 20×/0.50 NA objective (Plan Fluor; Nikon). All images were acquired using Nikon ACT-1 Version 2.63 software.