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A role for the laminin receptor in leukocyte chemotaxis
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 10(4) 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.
Insights
Polymorphonuclear cells (PMN) have a laminin receptor, crucial for their migration through basement membranes. This receptor facilitates cell attachment and chemotaxis, similar to metastatic tumor cells.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Leukocyte transmigration across basement membranes is vital for immune response.
- Polymorphonuclear cells (PMN) utilize basement membrane components like laminin and type IV collagen for migration.
- Previous research indicated PMN interaction with laminin and chemotaxis towards it.
Purpose of the Study:
- To determine if PMN possess a specific receptor for laminin.
- To characterize the binding affinity and site density of this receptor.
- To investigate the role of the laminin receptor in PMN function and extravasation.
Main Methods:
- Scatchard analysis using radiolabeled laminin to quantify binding sites.
- Utilizing a specific laminin fragment (C1) to confirm receptor binding.
- Immunoperoxidase staining with monoclonal antibodies (mAbLR) to localize the receptor on PMN.
- Chemotaxis assays with laminin, C1, and formyl peptides, assessing inhibition by mAbLR.
Main Results:
- PMN possess a single class of high-affinity laminin binding sites (Kd = 6.15 nM/L) with approximately 3.6 x 10^4 sites per cell.
- A laminin fragment (C1) lacking matrix binding regions but retaining the receptor-binding region also bound to PMN.
- Monoclonal antibodies against the laminin receptor inhibited PMN chemotaxis to formyl peptides, suggesting a general role in PMN migration.
- PMN exhibited chemotaxis towards both intact laminin and the C1 fragment.
Conclusions:
- PMN possess a specific, high-affinity receptor for laminin.
- This laminin receptor plays a significant role in PMN extravasation by mediating both attachment to the basement membrane and chemotaxis.
- The observed characteristics of PMN migration via the laminin receptor share similarities with the behavior of highly metastatic tumor cells.