RED CELL ANTIGEN

These are substances on the red cell membranes that are able to stimulate immuological response.
They are complex glycolipids or glycoproteins. There are about 300 identified red cell antigens but not all are clinically significant in blood transfusion/transplant medicine or for paternity dispute.

CHARACTERISTICS
NATURALLY OCCURING ANTIBODIES
Usually IgM
Optimun temperature of reaction below 30oC but have a wide range of tempt.
Cause red cell agglutination
Complement binding.
Does not cross the placenta.
Sensitive to 2 mercaptoethanol and dithiothreitol
Examples : ABO system, Ii system, P, MNSs and Lewis.

IMMUNE ANTIBODIES
Usually IgG
Optimum tempt. Is 37oC
Cause agglutination that is enhanced by anti IgG.
complement binding.
Crosses the placenta.
Examples; Rhesus system, Duffy system, Kell, Kidd
The following antigens are easily destroyed by enzyme treatment; MNS and Duffy.

ABO SYSTEM
STRUCTURE:
Backbone
NAcGal Gal NAcGlu Lewis a Gal L-Fucose
NAcGal or Gal
Subtypes A1, A2, A3, A4, A5,Ax, Ay.

OTHER GLYCOLIPOPROTEINS
P System P, P1, P2, Pk, p.antibody has high thermal range and may be IgG as in paroxysmal cold haemaglutinin disease.

LEWIS system:Le(a,b).Se.significant in paternity dispute.

MNS system:MN carried on glycophorin A and S on glycophorin B that are required for the invasion on plasmodium falciparum.Anti S may be immune.
Ii system: In chronic cold haemaglutinin disease, anti I in mycoplasma pneumoniae and anti-i in lymphoma

PROTEIN ANTIGEN
MNS
DUFFY:Fy(ab) a receptor for P. vivax and cytokine IL-8.
Kidd system: Jk(ab) gives transient antibodies.
Kell system: K(rare in black), k, Kp, Js, Kx on X chromosome. Lack in McLeod and CGD. K antigen is very antigenic.
Rh system.nomenclature, variants, absence-stomatocytosis, antigenicity