Blocking IL-1 limits blood-induced chondrocyte apoptosis. Representative photomicrographs of chondrocyte apoptosis in human articular cartilage explants cultured in medium (A) or exposed to 50% v/v whole blood (B-D) for 4 days. IL-1βmAb (C) or TNFαmAb (D) was added during blood exposure. Apoptosis of chondrocytes was determined by immunohistochemical staining with ssDNA (brown staining, indicated by arrow). Original magnification ×40.