Collagen-bound alpha(1)-microglobulin in normal and healed tissues and itseffect on immunocompetent cells

The mechanisms devoted to the protection of the extracellular matrix collag en from the inflammatory insult are not fully understood. We investigated t he presence of the immunosuppressive glycoprotein alpha(1)-microglobulin in healed tissues such as scars and periprosthetic membranes, comparing them with normal skin. Immunohistochemistry showed that alpha(1)-microglobulin w as mainly present along collagen fibrils and in the epidermis. The presence of this protein was confirmed by Western blot of the tissue homogenates, w hile ELISA showed lower levels in the healed tissues. In vitro, the purifie d alpha(1)-microglobulin bound collagen by a cooperative mechanism and atte nuated the collagen-induced activation of the mononuclear cells.