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Controversy surrounds the glycolipid iGb3. Our data show that humans do not express this lipid. This has important implications in natural killer T cell development, self-recognition, and transplantation. [ABSTRACT FROM AUTHOR]

Background: Many immunologically important interactions are mediated by leukocyte recognition of carbohydrates via cell surface receptors. Uncharacterized receptors on human natural killer (NK) cells interact with ligands containing the terminal Gal α(1,3)Gal xenoepitope. The aim of this work was to isolate and characterize carbohydrate binding proteins from NK cells that bind αGal or other potential xenoepitopes, such as N-acetyllactosamine (NAcLac), created by the deletion of α1,3galactosyltransferase (GT) in animals. Methods and results: Initial analysis suggested the human C-type lectin NKRP1A bound to a pool of glycoconjugates, the majority of which contained the terminal Gal α(1,3)Gal epitope. This was confirmed by high level binding of cells expressing NKRP1A to mouse laminin, which contains a large number of N-linked oligosaccharides with the Gal α(1,3)Gal structure. The consequence of removing the terminal αGal was then investigated. Elevated NAcLac levels were observed on thymocytes from GT−/− mice. Exposing NAcLac on laminin, by α-galactosidase treatment, resulted in a significant increase in NKRP1A binding. Conclusions: NKRPIA binds to the αGal epitope. Moreover, exposing NAcLac by removal of αGal resulted in an increase in binding. This may be relevant in the later phases of xenotransplant rejection if GT−/− pigs, like GT−/− mice, display increased NAcLac expression. [ABSTRACT FROM AUTHOR]