Regulation of inflammation by collagen-binding integrins α1β1 and α2β1 in models of hypersensitivity and arthritis

Adhesive interactions play an important role in inflammation by promoting leukocyte attachment and extravasation from the vasculature into the peripheral tissues. However, the importance of adhesion molecules within the extracellular matrix-rich environment of peripheral tissues, in which cells must migrate and be activated, has not been well explored. We investigated the role of the major collagen-binding integrins, alpha 1 beta 1 and alpha 2 beta 1, in several in vivo models of inflammation. mAb's against murine alpha 1 and alpha 2 were found to significantly inhibit effector phase inflammatory responses in animal models of delayed-type hypersensitivity (DTH), contact hypersensitivity (CHS), and arthritis. Mice that were al-deficient also showed decreased inflammatory responses in the CHS and arthritis models when compared with wild-type mice. Decreased leukocyte infiltration and edema formation accompanied inhibition of antigen-specific models of inflammation, as nonspecific inflammation induced by croton oil was not inhibited. This study demonstrates the importance in vivo of alpha 1 beta 1 and alpha 2 beta 1, the collagen-binding integrins, in inflammatory diseases. The study also extends the role of integrins in-inflammation beyond leukocyte attachment and extravasation at the vascular endothelial interface, revealing the extracellular matrix environment of peripheral tissues as a new point of intervention for adhesion-based therapies.