Cell adhesive, protein binding, and antigenic properties of laminin

The cell adhesive, protein-binding and immunological properties of laminin were studied. When present on a solid-phase, laminin promoted to some degree the adhesion of various types of cells including fibroblasts, but it was less active than insolubilized fibronectin, type I collagen, or type IV collagen. When laminin was present in solution, it promoted the adhesion of cells to surfaces that would otherwise be nonadhesive. No significant binding of laminin to type IV collagen could be demonstrated by affinity assays employing radioactively labeled ligands or enzyme-labeled antibodies. Binding of laminin to anti-laminin and to polyornithine could be readily demonstrated under the same conditions. The possible autoantigenicity of laminin was studied by immunizing mice with rat and mouse laminin. Rat laminin induced antibodies that reacted strongly with rat laminin and weakly with mouse laminin in enzyme immunoassay. Mouse laminin did not induce any detectable antibodies. These results confirm earlier work on cell adhesive properties of laminin but show that laminin is different from fibronectin adhesive properties of laminin but show that laminin is different from fibronectin in that laminin promotes adhesion of cells better when presented to the cells in a soluble form. They do not support the contention that laminin would bind directly to type IV collagen or that it would be autoantigenic.