Blood Groups & Blood Transfusion. By Dr. Ola Mawlana. Agglutinogens. Two antigens - type A and type B- occur on the surface of red blood cells in large proportion of human beings which causes most blood transfusion reactions.
Dr. Ola Mawlana
Two antigens - type A and type B- occur on the surface of red blood cells in large proportion of human beings which causes most blood transfusion reactions.
Two genes one on each two paired chromosomes determine the O-A-B blood type. Only one type on each of the two chromosomes.
Antibodies specific to the agglutinogens present in the plasma eg Anti-A and Anti-B
Origin of Agglutinins in the plasma
They are gamma globulins produced by the bone marrow and lymph glands, most of them are IgM and IgG immunoglobulin molecules
On mismatched blood transfusion, the anti-A or anti-B plasma agglutinins are mixed with red blood cells that contain A or B agglutinogens, as IgM has 10 binding sites and IgG has 2 binding sites, a single agglutinin can binds to 2 or more RBCs at the same time causing the cells to bind together by aglutinin leading to their clump (agglutination) and plugging of the blood vessels then attacked by phagocytic WBCs which causes hemolysis of RBCs.
Immediate intravascular hemolysis is less common than agglutination follwed by delayed hemolysis as it need high titer of antibodies for lysis to occur and IgM type which called hemolysin
Blood TypingThe RBCs are first separated from the plasma and diluted with saline and add one drop to a slide containig both Anti A and anti B.
There are 6 common types of Rh antigens C, D, E and c, d, and e the person who has a C antigen does not have c antigen. The D antigen is the most common and more antigenic than the other forms, A person has D antigen is +ve Rh while that does not have D antigen is -ve Rh
85% are Rh +ve
15% are Rh-ve
When RBCs containing Rh factor are injected to Rh -ve person the Rh agglutinins develop slowly reaching the maximum concentration in 2-4 months. With multiple exposure to the Rh factor an Rh-ve person becomes strongly sensitized to Rh factor.
On primary exposure of RH-ve person to Rh+ blood there is no immediate reaction, but Rh antibodies can develop in suffient quantities during the next 2-4 weeks to cause agglutination of the transfused cells that are still circulating in the blood ( delayed transfusion reactions), on repeated transfusion there is immediate transfusion reactions.
When a Rh +ve male married to Rh –ve female the fetus will inherited the Rh +ve from the father and the mother will develop anti Rh agglutinins from exposure to the fetus Rh antigen. In turn the mother agglutinin will diffuse through the placenta into the fetus and causes blood cells agglutination.
The mother’s antibodies pass through the placenta to the fetus causing agglutination of RBCs leading to their rupture with releasing of Hb into the blood, then the macrophage convert the Hb into bilirubin causing the yellow color of the skin( jaundice).
On transfusion of one blood type into another blood type recipient, the result will be agglutination of the donner’s RBCs as the plasma portion of the donner will be diluted by all the plasma of the recipient, conversely, the small amount of the infused blood does not significantly dilute the agglutinin in the recipient's plasma
- Kidney failure is the lethal effect of transfusion reaction.