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 in the
thymus
The thymus (: thymuses or thymi) is a specialized primary lymphoid organ of the immune system. Within the thymus, T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. The thymus ...
.
iGb3 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
iGb3 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 Major histocompatibility c ...
- 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,
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 used ...
, and
NMR
Nuclear magnetic resonance (NMR) is a physical phenomenon in which atomic nucleus, nuclei in a strong constant magnetic field are disturbed by a weak oscillating magnetic field (in the near and far field, near field) and respond by producing ...
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
Acetamides