Abstract
The distribution and number of mast cells at the site of adjuvant rat enthesis caused by the insertion of Achilles tendons were analyzed by light and electron microscopy. The light microscopic findings showed inflammatory cell infiltration (enthesitis) followed by new bone formation at the site of enthesis. Increasing numbers of mast cells were observed around the capillaries in the inflammatory granulation tissue formed at the enthesis. In addition, the mast cell count was increased in the marrow of newly formed bone. The electron microscopic findings demonstrated that the mast cells observed were closely related with fibroblasts and newly formed bone. These findings suggested that mast cells have important roles not only in immunological reactions but also in the process of new bone formation in the adjuvant enthesitis.
