Galactose-alpha-1,3-galactose: Possible Role in Red Meat Allergy

Abstract

Recent studies have indicated that patients who exhibit immediate hypersensitivity to red meat also demonstrate IgE-mediated immunoreactivity to oligosaccharide galactose-alpha-1,3-galactose (alpha-gal) [1]. Why and how this happens is unclear, though several groups seem interested in this phenomenon. It is possible that an evolutionary or developmental basis exists for this observation. The alpha-gal epitope is distinctive in its dispersal in mammals; it is generously expressed in non-primate mammalian, New World monkeys, and prosimians, where by contrast an IgG antibody binding to this epitope is produced naturally in humans, Old World monkeys, and apes [2]. Non-primate mammals, such as bovine and porcine species, contain a larger proportion of red meat (slow and intermediate fibers) than ground-based birds. Ground-based birds, chickens and turkeys, in contrast, contain a significant amount of white meat, especially in their chest muscles (fast fibers). Slow and intermediate muscle fibers exhibit a higher resistance to fatigue, require more oxygen supply, and therefore contain a more extensive vascular supply. Due to increased amounts of blood capillaries surrounding slow and intermediate muscle fibers, there is an increase of basement membrane (BM). Laminin, a glycoprotein present abundantly in the basal lamina layer of BM, has been shown to contain N-linked oligosaccharides in large amounts exhibiting the alpha-gal structure [3]. It is thereby assumed that red meat, primarily in non-primate mammals, will demonstrate a higher quantity of alpha-gal. The antibody against alpha-gal that is found naturally in non-immunocompromised humans, Old World monkeys, and apes is in the form of IgG and represents 1% of the immunoglobulins dispersed in these subjects [4]. IgG is the most abundant class of immunoglobulins found in the plasma and primarily functions to inhibit the infectivity and toxicity of viruses and toxins, respectively. IgG also works by activating complement and thereby facilitating the removal of pathogens by phagocytic ingestion. However, as discussed below, allergic and serious anaphylactic reactions often involve immunoglobulin E (IgE).