Presence of bone morphogenetic protein-2 (BMP2) during collagen-induced arthritis. Immunohistochemistry in the initial phase (a, b), with increasing severity (c-f), and in the destructive phase of collagen-induced arthritis (g, h) is shown. Severity scoring was done on sections stained with hematoxylin and eosin. Boxes indicate areas that are magnified in BMP2 stainings. Arrows indicate BMP2-positive cells in synovium. Bars = 200 μm (a, c, e, g) and 25 μm (b, d, f, h).