BLOOD GROUPS

PIO 201
MONDAY 2-4 PM
 OUTLINE
❑ ABO and Rh blood group systems

❑ Hazards and complications of blood

transfusions
 OBJECTIVES
At the end of this class, you should be able
to:
❑List and differentiate the blood groups
❑Explain the importance of cross matching
and blood transfusion
 Antigens and Antibodies
❑ Antigens are substances that the body does not recognize
as belonging to the “self” which trigger a defensive
response from the leukocytes of the immune system.
▪ Generally large proteins, but may include carbohydrates, lipids, and
nucleic acids.
❑ Antibodies (immunoglobulins) are proteins produced by
certain B lymphocytes (plasma cells).
▪ Attach to the antigens on the plasma membranes of the transfused
erythrocytes and cause them to adhere to one another.
 Antigens and Antibodies
❑ Antigens: isoantigens or agglutinogens
❑ Antibodies: isoantibodies or agglutinins
❑ Following a transfusion of incompatible blood, erythrocytes
with foreign antigens appear in the bloodstream and trigger
an immune response.
❑ More than 50 antigens have been identified on erythrocyte
membranes, but the most significant are classified in two
groups:
▪ the ABO blood group
▪ Rh blood group.
 Transfusion Reactions
• Antibodies attach to the antigens on the plasma membranes
of the transfused erythrocytes and cause them to adhere to
one another.
• Because the arms of the Y-shaped antibodies attach randomly
to more than one nonself erythrocyte surface, they form
clumps of erythrocytes - Agglutination.
• These clumps block small blood vessels throughout the body,
depriving tissues of oxygen and nutrients.
• As the clumps are degraded (hemolysis) their hemoglobin is
released into the bloodstream.
• This hemoglobin travels to the kidneys but excess hemoglobin
released can easily overwhelm the kidney’s capacity to clear
it, and the patient can quickly develop kidney failure.
 Definition of Terms
❑ Agglutination: collection of separate RBCs into clumps or
masses

❑ Agglutinogen: antigen, on the surface of the erythrocyte

❑ Agglutinin: antibody, found in the plasma

❑ Hemolysis: is the degradation of the erythrocyte clumps

 ABO Blood Group
❑ Discovery: Karl Landsteiner, an Austrian scientist, in 1901.
❑ Determined by the presence or absence of specific marker
molecules on the plasma membranes of erythrocytes
❑ ABO blood typing designates the presence or absence of
just two antigens, A and B.
❑ Both are glycoproteins.
▪ People whose erythrocytes membrane surface have A antigens are
blood type A,
▪ Those whose erythrocytes have B antigens are blood type B.
▪ People with both A and B antigens are blood type AB.
▪ People with neither A nor B antigens are designated blood type O.
❑ ABO blood types are genetically determined.
 ABO Blood Group
• Normally the body must be exposed to a foreign antigen
before an antibody can be produced.
• This is not the case for the ABO blood group. Individuals
with:
– Type A have preformed antibodies to the B antigen
circulating in their plasma. Anti-B (β-antibody) antibodies, will
cause agglutination and hemolysis if they ever encounter
erythrocytes with B antigens.
– Type B blood have pre-formed anti-A (α-antibody) antibodies.
– Type AB blood having both antigens do not have preformed
antibodies to either of these.
– Type O blood lack antigens A and B on their erythrocytes, but
both anti-A and anti-B antibodies circulate in their plasma.
 LANDSTEINER LAW
❑ The law states that if a particular
agglutinogen (antigen) is present in the
RBCs, corresponding agglutinin (antibody)
must be absent in the serum.
❑ If a particular agglutinogen is absent in
the RBCs, the corresponding agglutinin
must be present in the serum.
Antigen and Antibody present in ABO blood groups
 Rh Blood group
❑ Rh factor is an antigen present in RBC.
❑ Discovered by Landsteiner and Wiener in Rhesus monkey
and hence the name ‘Rh factor’.
❑ The Rh blood group is classified according to the
presence or absence of a second erythrocyte antigen
identified as Rh. Known is designated D.
❑ Those who have the Rh D antigen present on their
erythrocytes are described as Rh positive (Rh+) and
those who lack it are Rh negative (Rh−).
 Rh Blood group
❑ When identifying a patient’s blood type, the Rh group is
designated by adding the word positive or negative to the
ABO type.
▪ A positive (A+) means ABO group A blood with the Rh
antigen present
▪ AB negative (AB−) means ABO group AB blood without
the Rh antigen.
❑ In contrast to the ABO group antibodies, which are
preformed, antibodies to the Rh antigen are produced only
in Rh− individuals after exposure to the antigen -
Sensitization.
 Rh Blood group
• This occurs following a transfusion with Rh-incompatible
blood or with the birth of an Rh+ baby to an Rh− mother
• The Rh group is distinct from the ABOs, in spite of their
ABO blood type, there is a presence or absence of this Rh
antigen.
• Rh group system is also different from ABO group system
because, the antigen D does not have corresponding
natural antibody (anti-D).
• If Rh+ blood is transfused to a Rh− person, anti-D is
developed in that person.
• However, there is no risk of complications if the Rh +
person receives Rh− blood.
 DETERMINATION OF ABO GROUP
• A.k.a blood grouping, blood typing or blood matching.
• Agglutination occurs if an antigen is mixed with its
corresponding antibody.
– A antigen is mixed with anti-A or when B antigen is mixed with
anti-B.
• To determine the blood group of a person, a suspension of
one’s RBC and testing antisera are required.
• Suspension of RBC is prepared by mixing blood drops with
isotonic saline (0.9%)
• Test sera are: Antiserum A (anti-A or α-antibody),
Antiserum B, (anti-B or β-antibody)
 DETERMINATION OF ABO GROUP
• Method:
– One drop of antiserum A is placed on one end of a glass
slide (or a tile) and one drop of antiserum B on the
other end.
– One drop of RBC suspension is mixed with each
antiserum. The slide is slightly rocked for 2 minutes.
– The presence or absence of agglutination is observed by
naked eyes.
– Presence of agglutination is confirmed by the presence
of thick masses (clumping) of RBCs.
– Absence of agglutination is confirmed by clear mixture
with dispersed RBCs.
 MATCHING AND CROSS-MATCHING

❑ Blood typing is a laboratory test done to determine the blood

group of a person.
❑ When the person needs blood transfusion, another test called
cross-matching is done after the blood is typed.
❑ Cross-matching is done by mixing the serum of the recipient
and the RBCs of donor.
❑ Cross-matching is always done before blood transfusion.
❑ Matching = Recipient’s RBC + Test sera.
Cross-matching = Recipient’s serum + Donor’s RBC.
 TRANSFUSION REACTIONS DUE TO ABO
INCOMPATIBILITY
❑ In mismatched transfusion, the transfusion reactions occur
between donor’s RBC and recipient’s plasma.
❑ If the donor’s plasma contains agglutinins against
recipient’s RBC, agglutination does not occur because these
antibodies are diluted in the recipient’s blood.
❑ But, if recipient’s plasma contains agglutinins against
donor’s RBCs, the immune system launches a response
against the new blood cells.
❑ Donor RBCs are agglutinated resulting in transfusion
reactions.
❑ The reactions may be mild causing only fever and or may
be severe leading to jaundice, renal failure, cardiac shock
and death.
 TRANSFUSION REACTIONS DUE TO Rh
INCOMPATIBILITY
❑ A Rh- person receives Rh+ for the first time, and isn’t
affected much as the reactions don’t occur immediately.
❑ But the Rh antibodies develop within one month.
❑ The transfused RBCs, which are still present in the recipient’s
blood, are agglutinated but lysed by macrophage.
❑ So, a delayed transfusion reaction occurs but usually mild and
does not affect the recipient. However, antibodies developed
in the recipient remain in the body forever.
❑ So, when this person receives Rh+ blood for the 2nd time, the
donor RBCs are agglutinated and severe transfusion reactions
occur immediately.
❑ These reactions are similar to the reactions of ABO
incompatibility
 ERYTHROBLASTOSIS FETALIS
❑ Hemolytic disease of the newborn.
❑ Hemolytic disease is the disease in fetus and newborn,
characterized by abnormal hemolysis of RBCs.
❑ It is due to Rh incompatibility
❑ Hemolytic disease leads to erythroblastosis fetalis.
❑ Erythroblastosis fetalis is a disorder in fetus, characterized
by the presence of erythroblasts in blood.
❑ When a mother is Rh negative and fetus is Rh positive,
usually the first child escapes the complications of Rh
incompatibility.
 ERYTHROBLASTOSIS FETALIS
❑ Problems are rare in a first pregnancy, since the baby’s Rh+
cells rarely cross the placenta
❑ At the time of parturition, the Rh antigen from fetal blood
may leak into mother’s blood because of placental
detachment.
❑ During postpartum period, the mother develops Rh
antibody in her blood.
❑ With the 2nd Rh+ fetus, the Rh antibody from mother’s
blood crosses placental barrier and enters the fetal blood.
❑ This causes agglutination of fetal RBCs resulting in
hemolysis.
 ERYTHROBLASTOSIS FETALIS
❑ To compensate for this hemolysis, there is rapid production
of RBCs, not only from bone marrow, but also from spleen
and liver.
❑ Many large and immature cells in proerythroblastic stage
are
released into circulation.
❑ The agglutination and hemolysis can be so severe that
without treatment the fetus may die in the womb or shortly
after birth.
❑ Ultimately due to excessive hemolysis severe complications
develop: Severe anemia, Hydrops fetalis, Kernicterus
 ERYTHROBLASTOSIS FETALIS

❑ A drug known as (RhoGAM) Rh immune globulin, can

temporarily prevent the development of Rh antibodies in the
Rh− mother averting this fetal disease.
❑ RhoGAM antibodies destroy any fetal Rh+ erythrocytes that
may cross the placental barrier.
❑ RhoGAM is normally administered to Rh− mothers during
weeks 26−28 of pregnancy and within 72 hours following
birth.
❑ The introduction of RhoGAM was in 1968.
 References

❑ https://open.oregonstate.education/aandp/chapter/18-6-blo
od-typing/

❑ K Sembulingam. Essentials of Medical Physiology. Blood

Clotting Chapter 20