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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.

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Blood Groups & Blood Transfusion

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Blood Groups& Blood Transfusion


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

Titer of Agglutinins at Different Ages

  • Immediately after birth, the quantity of agglutinins in the plasma is zero.

  • 2-8 months the infant starts to produce agglutinins.

  • 8-10 years maximum titer, then gradually declines by age.

    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

Genetic Determination of the Agglutinogens

Relative Frequencies of the Different Blood Types

Agglutination Process in Transfusion Reactions

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.

Rh Blood Types

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

Rh Immune Response

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.

ErythroblastosisFetalis(Hemolytic disease of the newborn)

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 1st baby has no harm

  • 3% of the 2nd baby has erythroblastosis fetalis

  • 10% of the 3rd has the disease

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).

Clinical picture

  • Anemia

  • Enlarged liver and spleen

  • Nucleated blastic RBCs in the peripheral blood

  • Deposition of bilirubin in the neuronal cells leads to its destruction ( Kernicterous)

  • Treated by replacement by Rh -ve blood

  • Prevention by anti D at 28-30 w of gestation to Rh –ve mothers

Transfusion reactions resulting from mismatched blood type

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.

Thank you

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