Macrophages express a plasma membrane receptor for basement membrane laminin

Laminin, a noncollagenous extracellular matrix glycoprotein, can serve as an attachment factor for epithelial and endothelial cells to basement membrane collagen. The authors have observed that inflammatory macrophages have the capacity to bind exogenous laminin in a time-, temperature- and dose-dependent manner. The laminin binds to these cells via a specific plasma membrane receptor which is detectable on several macrophage subpopulations as well as isolated macrophage membranes. The isolated receptor is a trypsin-sensitive protein with an apparent molecular weight of 70,000 which binds laminin with relatively high affinity, Kd approximately equal to 4 X 10(-9) M. The inflammatory macrophages attach preferentially to a substrate of laminin compared to Type I or Type IV collagen. Thus, the authors postulate that during tissue inflammation macrophages utilize the laminin receptor to bind to vascular basement membranes.