Matching the ABO
Group Allows Safe
Transfusions
LEARNING OBJECTIVES
1.
Outline
the components of the ABO blood
group.
2.
Describe
the Rh blood group.
3.
explain
the consequences of ABO blood typing
for transfusions.
T
he surfaces of RBCs and of many other cells
contain
genetically
determined
molecules
called
antigens
, which are composed of glyco-
lipids and glycoproteins. These antigens occur
in various combinations. Based on
the presence or absence of these
antigens, blood can be categorized
into different
blood types
(blood
cells that have the same antigens).
There are at least 24
blood groups
(classification sys-
tem based on hereditary characteristics of the blood) and
more than 100 antigens on RBCs. The most common blood
groups are the ABO group and the Rh group (
Figure 10.8
).
antigen
(AN-ti-jen)
A substance that has
the ability to provoke
an immune response.
A
b o
and
rh
Blood Groups
are important in Determining
Blood Compatibility
The basis for the blood groups is the interactions between
the antigens on the surface of an RBC and the antibodies
circulating in the plasma.
Antibodies
are proteins in the
blood that can bind to specific antigens. In the ABO group,
there are two antigens (A and B) and two corresponding
antibodies (anti-A and anti-B) (see Figure 10.8b). People
with Type A blood usually have anti-B antibodies, and
people with Type B blood usually have anti-A antibodies.
When RBCs with a specific antigen come in contact with
a corresponding antibody (for example, A antigen with
anti-A antibody), the RBCs either clump together (
agglu-
tinate
) or burst (
hemolysis
). This reaction would happen
if blood from a type B donor was given to a recipient with
type A blood with anti-B antibodies.
The antigen-antibody reaction forms the basis of the
ABO blood typing test (Figure 10.8a). One drop of the
patient’s blood is mixed with anti-A serum and another
is mixed with anti-B serum. Both spots are examined
for clumping, and the appropriate blood type is assigned
based on the results.
InSight
B lo o d g r o u p s a n d
b l o o d t y p e s
Figure 10.8
Antigen-antibody reactions are essential in determin-
ing the compatibility of various blood types and in the
tests for blood types.
Antigen-antibody reactions:
Antigens are proteins on the RBC membrane
Antibodies are proteins in the blood that can bind to
specific antigens
• If an antigen combines with the corresponding antibody
(e.g., RBCs with A antigen combine with anti-A
antibodies), then the RBCs will clump together
(agglutinate) and burst, thereby releasing hemoglobin
(hemolysis).
T
a.
Antigen-antibody
reactions form the basis of
ABO blood typing test
Anti-A serum
Anti-B serum
Untreated
blood
Treated with
Treated with
anti-A serum
anti-B serum
Blood
type
AB
O
Blood type
>
DO
>
DO
O
Compatible donor blooc
types (no reaction)
A, O
B, O
A, B, AB
O
,
O
Incompatible donor
blood types (reaction)
B, AB
A, AB
-
A, B,
AB
A
B
previous page 331 Craig Freudenrich, Gerard J  Tortora   Visualizing Anatomy and Physiology   2011 read online next page 333 Craig Freudenrich, Gerard J  Tortora   Visualizing Anatomy and Physiology   2011 read online Home Toggle text on/off