Blood groups and blood types
Physiology Lab-7
May 2022
Asst. Lec. Zakariya Al-Mashhadani
PRINCIPLE
• A blood type (also called 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.
• 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.
Purpose of blood typing
• Blood transfusion is a life-saving procedure in all
cases of severe loss of blood, and in life-threatening
anemias. However, blood can only be given after
blood grouping which is an essential requirement
before blood is given to any individual
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. In your blood,
you have antibodies for the antigens you don't have.
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:
• 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”
APPARATUS AND MATERIALS
1. Microscope.
2.Sterile blood lancet, 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). These
Determining Your Own Blood Type
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 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.
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.
Why does the ABO-incompatibility rarely produce hemolytic
disease of the newborn?
• The ABO-incompatibility between the mother and fetus rarely causes 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
