Eosinophil interaction with antibody-coated, non-phagocytosable surfaces: changes in cell surface proteins.

Plasma membrane changes during the interaction of human eosinophils with large, antibody-coated, non-phagocytosable surfaces have been investigated in a model system. Human peripheral blood eosinophils were incubated with layers of agar into which teranus toxoid (ECF), were incorporated. Changes in organization of the eosinophil plasma membrane proteins during interaction with the agar layer were detected by lactoperoxidase-catalysed iodination with [125]iodide. A protein of apparent mol. wt 55 000 became newly accessible on the eosinophil surface as a specific consequence of interaction with antigen-antibody complexes in the agar layer. This protein appeared in the early attachnent phase of the interaction which preceded extracellular degranulation. Cytochalasin D enhanced its appearance, while Mg2+-deficiency prevented it. A second newly accessible protein of apparent mol. wt 58 000 was blocked when ECF was present and may therefore be a receptor for ECF. Other proteins of apparent mol. wt 68 000 and 46 000 newly appeared at the surface of eosinophils even after incubation in suspension, apparently as a consequence of the rapid cycling of membrane components which occurs in eosinophils.