The ratio of late to early events stimulated by the mast cell receptor for immunoglobulin E (IgE) correlated with the affinity of a ligand for the receptor-bound IgE. Because excess receptors clustered by a weakly binding ligand could hoard a critical initiating kinase, they prevented the outnumbered clusters engendered by the high-affinity ligands from launching the more complete cascade. A similar mechanism could explain the antagonistic action of some peptides on the activation of T cells.
Arthritis and Rheumatism Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892-1820, USA.
