Figure 1. Inflammation-induced osteoclast formation. (A) The inflammatory process in the gingiva in periodontitis sites consists of mononuclear leukocytes and a large number of newly formed blood vessels. On the surface of the alveolar bone, several mononucleated bone-resorbing osteoclasts are present. The biopsy is from a mink with severe periodontal disease. (B) The inflammatory process in the pseudomembrane present between the prosthesis and femur consists of an infiltrate of mononuclear leukocytes. On the surface of the bone tissue in the femur from a patient re-operated due to loosening of a hip prosthesis, several osteoclasts and a large number of Howship’s resorption lacunae (dashed arrow) can be observed. The photo is a kind gift from Dr. Christopher Collins, University of Bristol, UK, and is reproduced with his permission. (magnification not defined)