Aim = To prevent haemolysis of the transfused RBCs
To do so, 3 steps:
When blood is transfused into an individual with an incompatible blood type...
After transfusion, the plasma in the transfusion is so diluted
--> Agglutinins in plasma rarely causes agglutination
* i.e. the antibodies in the transfused plasma does not cause damage to recipient's own RBC
When recipient's plasma has agglutinins against the donor's RBC
--> Donor's RBC agglutinate and hemolyse
--> Free Hb liberated into plasma
--> Transfusion reaction
Thus,
Group O blood (with no RBC antigen but both anti-A and anti-B antibodies) can be given to anyone
* But Group O individual can only receive Group O blood
* O = Universal donor
Group AB blood (with both A and B antigen, but no antibodies) cannot be given to anyone other than group AB
* But Group AB individual can receive any group type
* AB = Universal recipient
NB:
In crossmatching, donor RBCs are mixed with recipient plasma on a slide and checked for agglutination
Methods available:
Involves donor's RBC being suspended in saline and tested against antibodies at room temperature
Used for detected IgM antibodies
* e.g. anti-A, anti-B, anti-Lewis, anti-P, anti-M, and anti-N
When RBC are suspended in solutions containing free ions
--> Electric repulsion (zeta potential) between cells occurs as a result of negatively charged surfaces
Repulsion is reduced by presence of albumin or enzyme treatment of RBC with papain
* Papain removes negatively charged carbohydrates (e.g. sialic acid) from the cell surface
Used to enhance agglutination
* Usually for IgG antibodies
Suspended red cells are used to enhance the activity of some antibodies
Used to provide a rapid and sensitive method for detecting most blood group antibodies
Used to detect incomplete IgG and IgM antibodies
* e.g. Kidd and Duffy antibodies
[KB2:p187]