Transcript Blood groups

BLOOD GROUPS
AGGLUTINOGENS (Antigens)
Complex oligosaccharide substances on the
surface of the RBC membrane
AGGLUTININS
Antibodies against agglutinogens
Present in plasma of individuals after birth
Two major blood group systems :
A
ABO system - 4 blood groups
B
AB
Rh system - Rh+ and Rh -
O
ABO system
Blood group
Agglutinogens
Agglutinins
(on RBC)
(in plasma)
A
A
Anti-B
B
B
Anti-A
AB
A, B
None
O
None
Anti-A, Anti-B
Inheritance of blood group antigens :
A & B - Mendelian dominant
O
- recessive
Phenotype
Genotype
A
AA - homozygous
AO - heterozygous
B
BB or BO
AB
AB
O
OO
H antigen
A antigen
B antigen
G
F
C
G
F
G
G
F
G
G
G
G
G
G
G
G
G
G
G
C
C
C
Ceramide
Galactose
G
Glucose
F
Fucose
Ganong – Fig.27-21
G
N-acetylgalactosamine
Rh system
Present only on RBCs
3 main types of antigens - C, D (most antigenic), E
If a person has antigen D
D+ve or Rh+ve
antigen D is absent
D-ve
or Rh-ve
Unlike ABO antibodies,
Anti-D antibodies do not develop without exposure of
a D-ve individual to D+ve RBC - by transfusion or during
pregnancy
Blood grouping
This is performed by mixing an individual’s red blood cells
with different types of antisera on a glass slide and seeing
whether agglutination occurs.
Antisera are commercially available
Clumping or
Agglutination of RBCs
Blood group - A+
What is the blood group ?
What is the blood group ?
What is the blood group ?
What is the blood group ?
Cross Matching
Donor’s RBCs
Recipient’s plasma
Blood samples to be
Serum containing
typed is added to the
Anti-A
Anti-B
antibodies
antibodies
drops of serum
Group A
Group B
Group AB
Group O
Agglutination
or clumping of
RBCs
Possible complications of blood transfusions
1. Incompatibility reactions
Antigens on donor’s RBCs
+
Antibodies in recipient’s
plasma
RBC Agglutination
Clumps
I/V haemolysis
release of Hb
may block
blood vessels
Haemoglobinaemia
and Jaundice
Renal failure
‘DEATH’
2. Fever - due to the presence of antibodies against
transfused WBCs and platelets
3. Allergic reactions - asthma
4. Circulatory overload
5. Iron overload
6. Air embolism - air can go into the circulation
7. Transmission of diseases - Malaria, hepatitis B, AIDS,
Syphilis
To avoid these complications “Autologous
transfusion” can be done.
Haemolytic disease of the newborn (HDN)
* ABO Incompatibility – common but mild
* Rh Incompatibility
Haemolytic disease of the newborn (HDN)
- Rh incompatibility When mother is Rh-ve and baby is Rh+ve
fetal blood can leak into maternal circulation at the time of the
delivery
mother is sensitized
formation of Anti-D antibodies in mother’s circulation
These antibodies can cross the placenta in subsequent
pregnancies
Haemolysis of fetal RBCs
‘Haemolytic disease of the new born’
(Erythroblastosis fetalis)
Complications1. If haemolysis is severe
death of the fetus in the uterus
2. Severe anaemia
3. Severe jaundice
4. Oedema (hydrops fetalis)
5. Destruction of neuronal cells due to deposition of bilirubin
nervous signs (Kernicterus)
‘Rh immune globulin (Rhogam) - anti-Rh antibodies’
injection prevents sensitization of mother’s immune system
with Rh+ antigen.