section 10.3
Cell-Surface Glycoproteins
167
TABLE 10-4
The C a rboh ydrate A n tig en ic D eterm in a n ts o f S elected B lo o d G rou p S u b sta n ces
Blood Group System
Sequence at Nonreducing Terminal of Oligosaccharide
ABO Locus
Aj antigen
Bj antigen
H or O antigen
FucaK
|Galj81-> 3GlcNAc/31—> 3Gal/31^ 4Glc-*
G alN A cal^
(In type A2, the linkage between Gal and GlcNAc is /31—>
4.)
Fucak
N|Gal/31-> 3GlcNAc/3—> 3Gal/3I^> 4G lc^
G a la l^
Fucal—>
2Gal/31-A 3GlcNAc/31-> 3Gal)31^ 4G lc^
The difference between the above antigens resides in the absence or presence of either N-acetylgalactosamine or galactose linked to the penultimate
galactose residue in a ( l—» 3) linkage. The oligosaccharide determinants occur in glycoproteins and in glycosphingolipids.
Lewis (L) Locus
GaljSk
Lea antigen
|GalNAc/Bl -» 3Gal/31 -> 4Glc-Cer
Fucal/*
Fuc a 1 —> 2Gal/3 k
Leb antigen
|GalNAc/3 1—> 3Gal/31
—> 4Glc-Cer
Fuca1
f
The Lewis antigens are not components of developng red blood cells. They are acquired as glycosphingolipids during circulation by adsorption from
plasma low- and high-density lipoproteins (Chapter 20).
P Locus
P antigen
PK antigen
I Locus
I antigen
i antigen
GalNAc/31—» 3Galal—>
4 G n \ß \->
4Glc/3l-Cer
G alal—» 4Gal/31—> 4Glc/31-Cer
Gal/31—>
4GlcNAc/3k
bGal/31^4-X*
Gal/31^ 4GIcNAc/31/^
Gal/31—> 4GlcNAc/31-> 3Gal/31^ 4-X*
X*=GlcNAc/31^ 3Gal/31-> 4GIc/31-Ccr
Gal = galactose,
GalNAc = N-acetylgalactosamine,
Glu = glucose,
GluNAc =N-acetylglucosamine,
Fuc = fucose
(
6
-deoxy-L-galactose),
Cer=ceramide (a sphingolipid).
precursor oligosaccharide. The classification of individu-
als into ABO types is based upon whether A or B antigens
are present or not; type A individuals have the A antigen,
type B, the B antigen, and type O, the H antigen, respec-
tively. Normally, an antigen and its specific antibody are
not present simultaneously. For example, individuals hav-
ing type A red blood cells possess anti-B antibodies; those
of type B possess anti-A antibodies; those of type AB have
neither of these antibodies; and those of type O have both
anti-A and anti-B antibodies (Table 10-5).
The antigenic variation of blood group substances is
due to specific glycosyltransferases (the primary gene
products) responsible for synthesis of the oligosaccharide
determinants (the secondary gene products).
Under appropriate experimental conditions, the blood
type of red blood cells can be changed by addition or
removal of specific carbohydrate residues. For exam-
ple, when type O red blood cells are incubated with the
galactose donor substrate (uridine diphosphate galactose)
and the specific a-galactosyltransferase enzyme, they are
