Laminin promotes the oxidative burst in human neutrophils via increased chemoattractant receptor expression

The extracellular matrix component, laminin, enhances the chemotactic responsiveness of polymorphonuclear leukocytes (PMN) in vitro, and low doses of chemoattractant substances augment the expression of PMN cell surface receptors for laminin. This study determined whether laminin acts in concert with chemoattractants to activate PMN. Laminin (5 to 100 micrograms/ml) stimulated lysozyme release and superoxide production in response to the chemoattractant, FMLP by as much as 69%. These results could be explained by changes in cell surface chemoattractant receptor expression in that incubation of normal PMN with laminin (5 to 75 micrograms/ml) increased the binding of 19 nM FML3H]P by 35 to 80%. This corresponded to as much as a 2.5-fold increase in the number of chemoattractant receptors/cells which had a lower average affinity. Laminin did not change the number or affinity of FML3H]P receptors present on organelle-depleted PMN cytoplasts, and the laminin-induced increase in FML3H]P receptors expressed on PMN from a patient with a specific granule deficiency was only 11 to 21% of that seen in normal PMN. These findings suggest that chemoattractants augment the expression of laminin receptors which mediate PMN attachment to basement membranes, followed by laminin-induced increases in the expression of cryptic chemoattractant receptors contained in intracellular granules, with resultant augmentation of the oxidative burst.