Alpha-gal syndrome: Unrecognized risks of a tick-bite-associated allergy in transplantation and cellular therapy.

Alpha-gal syndrome (AGS) is an immunoglobulin E (IgE)-mediated hypersensitivity to the oligosaccharide galactose-α-1,3-galactose, acquired through tick bites and increasingly recognized as a cause of allergic reactions to mammalian-derived medical products. Every major transplant modality creates distinct conditions under which sensitized patients may encounter alpha-gal, yet AGS knowledge has developed almost entirely outside the transplant literature. In conventional solid organ transplantation, risk arises primarily from perioperative exposures to porcine-derived heparin, gelatin-based hemostatic agents, and other mammalian-derived materials. In xenotransplantation, the well-characterized role of alpha-gal as the principal xenoantigen has driven the development of glycoprotein alpha-galactosyltransferase 1-knockout swine, but the distinct IgE-mediated pathway that defines AGS has received little attention. Hematopoietic stem cell transplantation introduces questions about conditioning-related immune remodeling of preexisting IgE sensitization, rabbit antithymocyte globulin as an underrecognized alpha-gal exposure, and transfusion-related alpha-gal syndrome when group B or AB plasma-containing blood products are transfused to susceptible patients. Cellular therapy manufacturing workflows that use animal-derived ancillary materials represent a further theoretical exposure pathway. Importantly, detectable anti-alpha-gal IgE does not invariably predict clinical reactivity, and the most appropriate clinical approach is risk stratification rather than reflexive exclusion. Generating the evidence base to support such stratification will require collaboration across allergy, transplant, and transfusion medicine.