Structure and function of IgE myeloma protein VL from an atopic patient

In a woman suffering from IgE myeloma, hay fever and polyvalent respiratory and skin allergy the IgE monoclonal protein VL was isolated and investigated with respect to structural and functional properties. The amino acid sequence of 22 isolated peptides--especially of the biologically significant C2-C3 part--corresponded with that originally described by Bennich et al. (Immunol Rev 1978;41:3-23; Prog Immunol 1974;13:49-58). However, in mass spectrometry the sugar residues on ASN 99 (219) and 252 (371) were deficient in sialic acids. The native IgE VL protein precipitated with high intensity all mannose-specific lectins as concanavalin A (Con A) and was able to release histamine after triggering by these lectins. The same lectins also elicited more histamine release and more positive skin reactions in atopic than in healthy persons. In sera from atopic patients the binding of IgE on Con A Sepharose 4B column was stronger than in normal persons. It is suggested that changes in the IgE glycosylation state may contribute to IgE-mediated pictures of clinical allergy by the nonimmunological pathway.