Fig 1: Neutrophil invasion and abundant NETs indicate immunothrombosis of BHV. (A) Immunohistochemical staining of the prosthetic thrombus identified platelets (CD41-positive staining), fibrin, and neutrophils (ELA2- and MPO-positive staining). CD45 staining was inconsistent. Macrophages (CD68), T cells (CD3) and B cells (CD19) were not detected. Magnification ×200. Scale bar = 100 µm; (B) Immunofluorescence staining showed the co-localization of citrullinated histone H3 with neutrophil elastase (ELA2) and nuclear dye (4′,6-diamidino-2-phenylindole, DAPI) within the thrombus indicating the formation of NETs. Sections without the primary antibody staining but still counterstained with DAPI were used as a negative control. Magnification ×200. Scale bar = 50 µm.