Dissociation of neutrophil aggregation, adhesiveness, and Fc receptor activity

Neutrophils that bear receptors for the Fc portion of immunoglobulin G have been demonstrated to be more active in assays of adherence, aggregation, and chemotaxis compared to Fc receptor‐negative cells. We examined the relationship of neutrophil Fc receptor activity and cell–cell adherence or aggregation induced by phorbol myristate acetate. In contrast to 1‐isoproterenol, isobutyl‐methyl‐xanthine, and dibutyryl cAMP, each of which inhibited Fc receptor activity and neutrophil aggregation, theophylline significantly impaired aggregation without affecting Fc receptor activity. The selective beta‐2 agonist, metaproterenol, and 8‐Bromo cAMP failed to inhibit Fc receptor activity or neutrophil aggregation. Three known inducers of neutrophil intracellular cyclic AMP, PGE₁, PGE₂, and cholera toxin, also did not inhibit Fc receptor activity. Inhibition of Fc receptor activity by 95% in the presence of purified Fc fragments did not affect neutrophil aggregation. Similarly suppression of Fc receptor activity by purified Fc fragments did not inhibit neutrophil adhesion to nylon fiber columns. These data demonstrate that the Fc receptor does not mediate phorbol myristate acetate‐induced cell–cell adhesion and is not necessary for optimal neutrophil adhesion to nylon fibers. Our results are consistent with the possibility that the reversible inhibitory activity of beta‐adrenergic agonists on rosette formation may be a steric effect rather than a metabolic effect. These data tend to dissociate Fc receptor activity, neutrophil aggregation, and adhesion and support the hypothesis that the Fc receptor may be a marker of neutrophil heterogeneity rather than a component necessary for optimal neutrophil aggregation or adhesion.