RBC antigens and antibodies

Red cell antigens

• Over 400 RBC antigens have been described
• Most are inherited in a simple Mendelian fashion

RBC antigens are important because

• Individuals lacking in a particular antigen may produce antibodies reacting with that antigen
• Most important RBC antigens are ABO and Rhesus
• Others are less important because
  * Weak antigen
  * Antibodies develop only after multiple exposures
  * e.g. Kell, P, Lewis, MNS, Kidd, Lutheran system

Red cell antibodies

• Most important naturally occuring RBC antibodies
  = Anti-A and anti-B antibodies
  * Mostly IgM
  * Does not cross placenta
• Most important RBC antibodies that occurs after exposure
  = Rhesus
  * Mostly IgG
  * Crosses placenta

Other notes

Kell system

Kell system is the 3rd most important system after ABO and Rh systems

K antigen is present on RBC, leukocytes, and platelets

Low frequency
--> Only cause iso-immunization in patients who have had multiple blood transfusion