Transcript Blood Groups & Blood Transfusion

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.
Two genes one on each two paired chromosomes determine the
O-A-B blood type. Only one type on each of the two
chromosomes.
Agglutinins
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
Genotypes
OO
OA or AA
OB or BB
AB
Blood Types
O
A
B
AB
Agglutinogens Agglutinins
Anti-A& Anti B
A
Anti-B
B
Anti-A
A and B
-
Relative Frequencies of the Different Blood Types
O
47%
A
B
AB
41%
9%
3%
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 Typing
The 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.
Red blood cell types
Anti-A
Anti-B
O
-
-
A
+
-
B
-
+
AB
+
+
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.
Erythroblastosis Fetalis
(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