Isoglobotriosylceramide, Gal(α1→3)Gal(β1→4) Glcβ(1→1) Cer, abbreviated as

iGb3 Isoglobotriosylceramide, Gal(α1→3)Gal(β1→4) Glcβ(1→1) Cer, abbreviated as iGb3, is an iso-globo-series of glycosphingolipid, which mysteriously disappeared in most mammals studied (pig, mouse, and human), except trace amount reported i ...

, is an iso-globo-series of

glycosphingolipid Glycosphingolipids are a subtype of glycolipids containing the amino alcohol sphingosine. They may be considered as sphingolipids with an attached carbohydrate. Glycosphingolipids are a group of lipids (more specifically, sphingolipids) and are a ...

, which mysteriously disappeared in most mammals studied (pig, mouse, and human), except trace amount reported in the

thymus The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, thymus cell lymphocytes or ''T cells'' mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. ...

was discovered in canine and rat intestines among iso-globo-series of glycosphingolipids. First NMR spectrums for standard iGb3 were published by Dr. Tomoya Ogawa. The physiological function of

is not clear. It has been identified as a

CD1d CD1D is the human gene that encodes the protein CD1d, a member of the CD1 (cluster of differentiation 1) family of glycoproteins expressed on the surface of various human antigen-presenting cells. They are non-classical MHC proteins, related to ...

- presented self-antigen for an innate type of immune cells termed as Natural Killer T (NKT) cells. Extensive biochemical studies by multiple methods including

HPLC High-performance liquid chromatography (HPLC), formerly referred to as high-pressure liquid chromatography, is a technique in analytical chemistry used to separate, identify, and quantify each component in a mixture. It relies on pumps to pa ...

mass spectrometry Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is use ...

, and

NMR Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with ...

did not lead to positive finding of iGb3 in major organs of mouse, pig, and human species, except trace amount in thymus and immune cells, suggesting a selection pressure during evolution. Obviously, the immune selection pressure against iGb3 is mechanistically different from the well known anti-alpha-Gal antibodies, which caused the loss of alpha1,3-galactose epitope on glycoproteins in humans, apes, and old world monkeys.Macher BA, Galili U. The Galalpha1,3Galbeta1,4GlcNAc-R (alpha-Gal) epitope: a carbohydrate of unique evolution and clinical relevance. Biochim Biophys Acta. 2008 Feb;1780(2):75-88. The disappearance of iGb3 in pig and mouse species cannot be attributed to anti-alpha-Gal antibodies which are absent in these animals.

References

{{reflist, 35em Glycolipids