BLOOD GROUPS

PHYSIOLOGY STUDENT LECTURE (MLS &

NURSING)
BY
DR ADEBAYO
 Importance of Blood
Grouping
Blood Transfusion
• Blood transfusion is a life-saving procedure in which lost blood is
replaced in cases of severe loss of blood, and in life-threatening
anemia.

NOTE
Blood can only be given after blood grouping which is an essential
requirement before blood is given to any individual. Giving blood to any
patient without proper grouping can lead to death of the patient.
 PRINCIPLE
• Determination of ABO blood groups depends upon the
immunological reaction between antigen and antibody.
• Landsteiner found two antigens on the surface of RBCs and named
them as A antigen and B antigen.
• A blood group is a classification of blood based on the presence or
absence of inherited antigenic substances on the surface of red
blood cells (RBCs).

• Blood is characterized into different blood groups, based on the

presence or absence of these antigens or agglutinogens because
of their capacity to cause agglutination of RBCs.
 ANTIGEN
An antigen is a large protein
molecule capable of
inducing an immune
response in the body by the
production of antibodies.
 ANTIBODY

• An antibody is a protein component of the immune

system that circulates in the blood, recognizes foreign
substances like bacteria and viruses, and neutralizes
them. After exposure to a foreign substance, called an
antigen, antibodies continue to circulate in the blood,
providing protection against future exposures to that
antigen.
• The ABO blood group is characterized by two glycolipid
antigens, called A and B – depending on whether the
RBCs have none, only one or both antigens, blood
groups are distinguished as type O, type A, type B, or
type AB.
 Agglutinins of ABO System
• Blood plasma contains antibodies or agglutinins that react with
non-self antigens.

• They are absent in a newborn; the ABO antibodies start appearing in

the plasma by the age of 3–4 months due to cross reactivity of
ABO antigens present in naturally occurring bacteria, viruses, pollen,
etc. present in the environment.

• These antigens are absorbed into blood and stimulate the formation
of antibodies against antigens not present in the infants’ red
cells, i.e. those antigens that are recognized as “non-self” by the
body’s immune system.

• Because the resulting antibodies are large IgM-type molecules that

cannot cross the placenta, incompatibility between mother and
foetus is not a common problem.
 Agglutination
• If someone receives blood of the wrong type, the worst problem is
the reaction of the recipient's antibodies on the donor's RBCs.

• When the body encounters a foreign antigen, agglutination occurs.

• Agglutination is the clumping of RBCs due to binding of antibodies

(part of the immune system) to antigen, and causes blockage of
blood vessels and eventually death.
Blood Groups
 RH factor
• In addition to antigens of ABO system, the red cells of humans also contain an additional antigen,
called Rh antigen (or Rh factor).

• There are several varieties of Rh antigen—C, D, E, c, d, and e—but the D antigen is the most
common, and antigenically, the most potent. Therefore, Rh +ve persons are also called D +ve and
Rh –ve are called D –ve.

• Persons whose red cells contain this additional antigen are called “Rh positive” ( Rh +) while
those who lack this antigen are called “Rh negative” (Rh –).

• However, there are no naturally occurring antibodies against Rh (D) antigen.

• The Rh (D) antigen is not present in body fluids and tissues, but only on red cells.
Clinical Significance of Rh factor

• Although there are no natural anti-Rh antibodies, and

they never develop spontaneously, they can be produced
only in Rh –ve persons. This can happen in either of 2
ways:
1. Transfusion
2. Pregnancy
 Clinical Significance of Rh
factor
• In transfusions: When an Rh –ve person receives Rh +ve blood,
there is no immediate reaction since there are no antibodies. But
during the next few weeks/months, he/she may produce anti-Rh
antibodies that will remain in the blood. (Even 0.5 ml of Rh +ve
blood is enough to produce immune response). However, if within a
few weeks, or even years later, a second Rh +ve blood is injected,
the newly donated red cells will be agglutinated and hemolysed,
thus resulting in a serious transfusion reaction.
 In pregnancy: The most common problem due to Rh incompatibility
may arise when an Rh –ve mother (phenotype dd) carries an Rh +ve
fetus
• Normally, no direct contact occurs between maternal and fetal
bloods. However, if a small amount of Rh +ve blood leaks (at the
time of delivery) from the fetus through the placenta into the
mother’s blood, the mother’s immune system will start to make anti-
Rh antibodies.

• As a result, some mothers develop high concentration of anti-Rh

antibodies during the period following delivery. Therefore, the
first-born baby will not be affected.
• However, during the second and
subsequent pregnancies, the
mother’s anti-Rh antibodies cross
the placental membrane into the
fetus where they cause
agglutination and hemolysis. The
clinical condition that develops in
the fetus is called “hemolytic
disease of the newborn (HDN)’
or “erythroblastosis fetalis”
 How can hemolytic disease of the newborn be
prevented? What is the treatment of severe
HDN?

• The condition can be prevented by desensitizing all Rh –ve mothers

by giving them injections of massive doses of anti-Rh antibodies
called Rho(D) immune globulin after every abortion, miscarriage, or
delivery.
• These antibodies bind to and inactivate the fetal Rh antigens (on
fetal red cells) present in maternal circulation. In this way, the Rh
antigens from the mother’s blood are cleared (removed) before they
have had time to stimulate production of anti-Rh antibodies.
 TRANSFUSION REACTION
Transfusion reactions are the adverse reactions in the
body, which occur due to transfusion error that involves
transfusion of incompatible (mismatched) blood. The
reactions may be mild causing only fever and hives (skin
disorder characterized by itching) or may be severe leading
to renal failure, shock and death.
 Signs and Symptoms of
Transfusion Reactions
1. Non-hemolytic transfusion reaction

Non-hemolytic transfusion reaction develops within a few

minutes to hours after the commencement of blood
transfusion. Common symptoms are fever, difficulty in
breathing and itching.
2. Hemolytic transfusion reaction

Hemolytic transfusion reaction may be acute or delayed.

a) The acute hemolytic reaction occurs within few minutes of
transfusion. It develops because of rapid hemolysis of donor’s RBCs.
Symptoms include fever, chills, increased heart rate, low blood
pressure, shortness of breath, bronchospasm, nausea, vomiting, red
urine, chest pain, back pain and rigor. Some patients may develop

pulmonary edema and congestive cardiac failure.

b) Delayed hemolytic reaction occurs from 1 to 5 days after
transfusion. The hemolysis of RBCs results in release of large amount
of hemoglobin into the plasma.

This leads to the following complications:

1. Jaundice

Normally, hemoglobin released from destroyed RBC is degraded and

bilirubin is formed from it. When the serum bilirubin level increases
above 2 mg/dL, jaundice occurs.
2. Cardiac Shock

Simultaneously, hemoglobin released into the plasma increases the

viscosity of blood. This increases the workload on the heart leading to
heart failure. Moreover, toxic substances released from hemolyzed cells
reduce the arterial blood pressure and develop circulatory shock.

3. Renal Shutdown

Dysfunction of kidneys is called renal shutdown. The toxic substances

from hemolyzed cells cause constriction of blood vessels in kidney.
 Materials For Determining Blood Group

1. Microscope.
2. Sterile cotton/ gauze swabs, Alcohol and Toothpicks.
3. Clean, dry microscope slides.
4. Anti-A serum: [contains monoclonal anti-A antibodies (against
human).
5. Anti-B serum: [contains monoclonal anti-B antibodies (against
human).

6. Anti-D (anti-Rh) serum: [Contains monoclonal anti-Rh (D) antibodies

(against human).
 Determining Your Own Blood Group

1. Clean your finger with alcohol and let dry.

2. Prick finger with lancet, near the tip but not too close to the nail.
You will need three fairly large drops of blood. Prick so that blood
flows freely. Try squeezing up from your wrist if blood does not
flow after pricking finger.
3. Use one slide for ABO typing and Rh factor. Place three drops of
blood on the slide, add the appropriate typing serum, and
determine your blood type. Be sure the serum dropper does not
touch the drop of blood. Results should be readable in about a
minute.
Figure above: Mixing the anti-serum with the blood sample to
determine blood type.
 OBSERVATIONS AND RESULTS

• It is essential that you should be able to distinguish between

“agglutination” and “no agglutination”. The features of each
are:
1. If agglutination occurs, it is usually visible to the naked eye. The
hemolysed red cells appear as isolated (separate), dark-red
masses (clumps) of different sizes and shapes.

2. There is brick-red coloring of the serum by the hemoglobin

released from ruptured red cells.
 Anti-A Anti-B Anti-D

4
 What is cross matching?

• In transfusion medicine, refers to the test that is

performed prior to a blood transfusion in order to
determine if the donor's blood is compatible with the
blood of an intended recipient.
• Cross-matching is also used to determine compatibility
between a donor and recipient, in organ transplantation
or blood transfusion.
 What is meant by the terms universal donor
and universal recipient?

• Since type O persons do not have either A or B antigens

on their red cells, they are called “universal donors”
because their blood can, theoretically, be given to all 4
blood types.
• Type AB persons are called “universal recipients”
because they do not have circulating agglutinins in their
plasma and can, therefore, receive blood of any type.
 Why does the ABO-incompatibility rarely
produce hemolytic disease of the newborn?

• The ABO-incompatibility between the mother and fetus

rarely causes Hemolytic disease of the newborn (HDN).

• The reason is that the anti-A and anti-B (anti-ABO)

antibodies belong to IgM type of gamma globulins (big
size) that do not cross the placenta.
Notes:
• To provide maximum benefit from each blood donation and to extend
shelf-life, blood banks fractionate some whole blood into several products.
The most common of these products are packed RBCs, plasma,
and platelets.
• With regard to transfusions of packed red blood cells, individuals with
type O Rh D negative blood are often called universal donors, and those
with type AB Rh D positive blood are called universal recipients.

• With regard to transfusions of plasma, this situation is reversed. Type O

plasma, containing both anti-A and anti-B antibodies, can only be given to O
recipients. The antibodies will attack the antigens on any other blood type.
Conversely, AB plasma can be given to patients of any ABO blood group
due to not containing any anti-A or anti-B antibodies.
Thank you