LAMININ RECEPTOR IN LEUKOCYTES

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Previous studies on the mechanism of leukocyte traversal of basement membranes showed that rabbit peritoneal exudate 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 I125-laminin indicate a single class of saturable high affinity binding sites (kd = 6.15 nM/L) on PMN and 3.6 x 10,000 sites per cell. A chymotryptically derived fragment of laminin, C1 which retains the cell binding site gave similar results. Immunoperoxidase studies using monoclonal antibodies to the laminin receptor indicated the presence of the receptor on PMN cell surfaces. PMN 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 the monoclonal antibodies, 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.