α2-Macroglobulin is found abundantly in plasma and interstitial fluids. The protease-α2-M balance plays an important role in mediating inflammatory tissue destruction. Serum levels of α2-M and protease-α2-M complexes are increased in patients with sepsis, emphysema, periodontitis, rheumatoid arthritis, and other inflammatory diseases, and oxidant inactivation of α2-M may contribute to tissue destruction during inflammation.