Galactose-α-1,3-galactose, commonly known as alpha gal and the Galili antigen, is a disaccharide (a type of carbohydrate) formed from two galactose molecules.

Biology

Galactose-α-1,3-galactose is found in most mammalian cell membranes. It is not found in catarrhines, including humans, who have lost the glycoprotein alpha-1,3-galactosyltransferase (GGTA1) gene.Singh, S., Thompson, J. A., Yilmaz, B., Li, H., Weis, S., Sobral, D., Truglio, M., Aires da Silva, F., Aguiar, S., Carlos, A. R., Rebelo, S., Cardoso, S., Gjini, E., Nuñez, G., & Soares, M. P. (2021). Loss of α-gal during primate evolution enhanced antibody-effector function and resistance to bacterial sepsis. Cell Host & Microbe, 29 (3). https://doi.org/10.1016/j.chom.2020.12.017

Anti-alpha gal immunoglobulin G (IgG) antibodies are some of the most common in humans. Regular stimulation from gut flora, typically initiated within the first six months of life, leads to an exceptionally high titre of around 1% of all circulating IgG.

Human reaction to alpha gal has beneficial uses as a vaccine adjuvant and for enhancing wound healing.

Allergy

Alpha-gal syndrome is an allergic reaction to the carbohydrate. It is caused by tick bites.

Alpha gal has been suggested to play a role in an immunoglobulin E-specific allergic response to some meats. While this allergic response is quite well documented, there is significant discrepancy between laboratory tests and clinical findings, indicating that much research must still be done on the alpha gal mechanism of action and related tests. Recent studies are showing increasing evidence that this allergy may be induced by the bite of the lone star tick (Amblyomma americanum)"Bad bite: Doctors see surge of sudden meat allergies caused by ticks that are spreading in US" USNews, July 7, 2014 in North America and the castor bean tick (Ixodes ricinus) in Sweden.

Xenotransplantation

The human immune system recognizes alpha gal as a foreign substance and produce xenoreactive immunoglobulin M (IgM) antibodies, leading to organ rejection after xenotransplantation.

A bacterial α-galactosidase that efficiently removes linear alpha gal ends from molecules has been identified. It could be useful for xenotransplantation in the future.

See also Alpha-gal allergy Galactose

References

External links GGTA1 Pseudogene