Binding of immunoglobulin classes and subclasses to human neutrophils and eosinophils

A comparative study of membrane expression of immunoglobin (Fc) receptors on human eosinophils and neutrophils has been undertaken using human IgG-1, IgG-2, IgG-3, IgG-4, IgA-1, IgA-2, IgM, IgD and IgE myeloma proteins. Sheep erythrocytes (E) coated with either human IgG-1, IgG-2, IgG-3 or IgG-4 myeloma proteins formed rosettes with human neutrophils and eosinophils. Proportionally more (1 1/2-2 times) rosettes were observed with neutrophils compared to eosinophils. In contrast, E-IgE bound to eosinophils (but not to neutrophils) to a degree that was comparable to E-IgG-1. Although IgG and IgE rosettes were inhibited by aggregates prepared from their corresponding myeloma protein there was no evidence that eosinophils and neutrophils have distinct receptors for IgG subclasses. Cells from four patients with hypereosinophilia were separated on density (metrizamide) gradients. The percentages of E-IgG-1 and E-IgE rosettes with normal- and light-density eosinophils were similar. Neutrophils, but not eosinophils, also bound significantly more E-IgA-1 and E-IgA-2 than the E-human albumin (E-Alb) control. In contrast, neutrophil and eosinophil rosette formation with E-IgM and E-IgD was not significantly different from E-Alb or E alone. These experiments indicate that human neutrophils and eosinophils bind homologous IgG subclass myeloma proteins, eosinophils, but not neutrophils, bind E-IgE with a similar avidity to that observed with E-IgG1, neutrophils, but not eosinophils, readily express demonstrable receptors for IgA-1 and IgA-2 and neither neutrophils nor eosinophils form E-IgM or E-IgD rosettes in greater numbers than the E-Alb controls.