A Role for the Laminin Receptor in Leukocyte Chemotaxis

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Abstract
Previous studies on the mechanism of leukocyte traversal of basement membranes showed that rabbit peritoneal exudate polymorphonuclear cells (PMN) preferentially used laminin, a major constituent of basement membrane, to attach to another component, type IV collagen. PMN also responded chemotactically to nanomolar levels of laminin. We have now determined that PMN possess a receptor for laminin. Scatchard analysis using 125I laminin indicates a single class of saturable high affinity binding sites (kd = 6.15 nM/L) on PMN and 3.6 x 104 sites per cell. A chymotryptically derived fragment of laminin, C1, which lacks both the long arm and the globular end regions of the short arm (i.e., matrix binding sites) but retains the laminin receptor binding region, gave similar results. Immunoperoxidase studies using monoclonal antibodies to the laminin receptor (mAbLR) indicated the presence of the receptor on the surface of PMN. These cells responded chemotactically to nanomolar levels of C1 and laminin, a result consonant with binding data. PMN chemotaxis to a formyl peptide was markedly inhibited by mAbLR, suggesting that the laminin receptor may be required for PMN chemotaxis in general. Our results suggest that PMN extravasation across basement membranes is aided both by reversible attachment of the cells to laminin in the matrix and by chemotaxis to a gradient of soluble intact and possibly degraded laminin. These characteristics have much in common with those of highly metastatic tumor cells.