Identification of IgE-binding proteins in soy lecithin

Int Arch Allergy Immunol. 2001 Nov;126(3):218-25. doi: 10.1159/000049517.

Abstract

Background: Soy lecithin is widely used as an emulsifier in processed foods, pharmaceuticals and cosmetics. Soy lecithin is composed principally of phospholipids; however, it has also been shown to contain IgE-binding proteins, albeit at a low level. A few clinical cases involving allergic reactions to soy lecithin have been reported. The purpose of this investigation is to better characterize the IgE-binding proteins typically found in lecithin.

Methods: Soy lecithin proteins were isolated following solvent extraction of lipid components and then separated on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The separated lecithin proteins were immunoblotted with sera from soy-sensitive individuals to determine the pattern of IgE-binding proteins. The identity of IgE-reactive bands was determined from their N-terminal sequence.

Results: The level of protein in six lecithin samples obtained from commercial suppliers ranged from 100 to 1,400 ppm. Lecithin samples showed similar protein patterns when examined by SDS-PAGE. Immunoblotting with sera from soy-sensitive individuals showed IgE binding to bands corresponding to 7, 12, 20, 39 and 57 kD. N-terminal analysis of these IgE-binding bands resulted in sequences for 3 components. The 12-kD band was identified as a methionine-rich protein (MRP) and a member of the 2S albumin class of soy proteins. The 20-kD band was found to be soybean Kunitz trypsin inhibitor. The 39-kD band was matched to a soy protein with unknown function.

Conclusions: Soy lecithin contains a number of IgE-binding proteins; thus, it might represent a source of hidden allergens. These allergens are a more significant concern for soy-allergic individuals consuming lecithin products as a health supplement. In addition, the MRP and the 39-kD protein identified in this study represent newly identified IgE-binding proteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Allergens / immunology*
  • Antigen-Antibody Complex / immunology
  • Child
  • Female
  • Humans
  • Hypersensitivity / immunology*
  • Immunoblotting
  • Immunoglobulin E / immunology*
  • Male
  • Middle Aged
  • Phosphatidylcholines / immunology*
  • Soybean Proteins / immunology
  • Soybeans / immunology*

Substances

  • Allergens
  • Antigen-Antibody Complex
  • Phosphatidylcholines
  • Soybean Proteins
  • Immunoglobulin E