Serum lysozyme (muramidase) activity in dogs with neoplastic disease

The lysozyme (muramidase) activity was measured in the sera of 84 dogs with neoplastic disease. Neoplasms included 32 lymphomas, 13 primary bone neoplasms, 5 melanomas, 5 thyroid neoplasms, 9 soft tissue sarcomas, 5 mast cell sarcomas, and 15 carcinomas. The sera from 21 healthy dogs served as control. Dogs with neoplastic disease had significantly (P less than 0.005) higher serum lysozyme activity than did the healthy controls. For lymphosarcoma, dogs with clinical signs of systemic disease had significantly higher serum lysozyme activity than did dogs without clinical signs. For bone neoplasms, dogs with metastatic disease had higher serum lysozyme activity than did dogs without metastasis. Increased lysozyme activity may be a useful marker of macrophage-mediated host responses to neoplasms in dogs.