Galactose-α-1,3-galactose, commonly known as alpha gal and the Galili antigen, is a carbohydrate found in most mammalian cell membranes.

Their immune systems recognize it as a foreign body and produce xenoreactive immunoglobulin M (IgM) antibodies, leading to organ rejection after transplantation.

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.

[9] A bacterial α-galactosidase that efficiently removes linear alpha gal ends from molecules has been identified.

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