Role of multinuclear cells in granulation tissue in osteomyelitis: immunohistochemistry in 66 patients.

We investigated the origin of multinuclear cells (MNCs) in the granulation tissue in osteomyelitis by immunohistochemical techniques in 66 patients. 12 samples were analyzed for the presence of CD68, cathepsin K, CD11b and tartrate-resistant acid phosphatase (TRAP) activity. Many MNCs were present in the granulation tissue adjacent to a sequestrum. MNCs in contact with the sequestrum were also noted, however, no osteoblasts were found. Immunohistochemically, CD68, cathepsin K and TRAP were strongly expressed in most of the MNCs, while CD11b positive cells were not found. MNCs remote from and in contact with the sequestrum showed the same immunohistochemical features which are characteristic of osteoclasts. Further, MNCs in contact with the sequestrum had originally developed in the granulation tissue and directly infiltrated towards the sequestrum without cell-to-cell interaction with osteoblasts.