Mechanisms of passive sensitization. IV. Dissociation of IgE molecules from basophil receptors at acid pH

The mononuclear cell fraction of human leukocytes was exposed to different pH at 0°C and the presence of cell bound IgE molecules on basophil granulocytes was examined by autoradiography. The results showed that both cell bound normal IgE and E myeloma protein bound to the basophils by passive sensitization dissociated from the cells upon exposure to pH 4 or lower. The receptor molecules on basophils were not degraded by the treatment. Basophils exposed to acid pH combined more IgE than untreated cells upon incubation with E myeloma protein at neutral pH. The results indicated that the binding between IgE and receptor molecules was reversible and did not involve a covalent bond.