HUMAN BIOLOGY

BLooD 147

What is a blood type?

• Like all cells, red blood cells bear genetically determined “self”
  markers on their surface. Some of these markers determine a
  person’s blood type.


• Each type of marker may have several forms, which are
  collectively called a blood group.


• Major blood groups include the ABO group and the Rh group.


• When incompatible blood types mix, an agglutination response
  occurs in which antibodies cause potentially fatal clumping of
  red blood cells.

taKe-Home message

ABO blood typing

Chemical analysis to deter-

mine which self marker

or markers from the ABO

blood group occur on a per-

son’s red blood cells.

agglutination Clumping of

red blood cells when incom-

patible blood types mix.

B

the ”foreign” cells and cause them to clump. The clumps

can clog small blood vessels, severely damaging tissues

throughout the body and sometimes even causing death.

some people bank their own blood

as “transfusion insurance”

Blood supplies at blood banks and in hospitals are carefully

typed and screened for viruses or other disease-causing

agents. Despite safeguards, however, it’s increasingly com-

mon for people to bank their own blood in advance of a

planned surgery that may require

a transfusion. Such an autologous

(“from one’s self”) transfusion avoids

any chance of receiving contami-

nated or mismatched blood.

We turn next to the Rh blood

group. As you’ll see, agglutination

is also a danger when mismatched

Rh blood types mix.

Figure 8.5 Animated! Mixing incompatible blood types causes

agglutination, or clumping. A Example of an agglutination reaction.

This diagram shows what happens when type B blood is transfused

into a person who has type A blood. B What an agglutination reaction

looks like. In the micrograph on the left, commingled red blood cells

are compatible and have not clumped. The cells on the right are

a mix of incompatible ABO types, and they have clumped together.

Donated blood is typed in order to avoid an agglutination response

when the blood is transfused into another person. (© Cengage Learning)

Compatible blood cells Incompatible blood cells

Donor with

type B blood

Antigen B

Antibody to

type A blood

Antibody to

type B blood

Red blood cells from

donor clump

(agglutinate)

Red blood cells usually

burst Clumping blocks blood flow

in capillaries

Oxygen and nutrient supply

to cells and tissues is

reduced

Side effects disrupt kidney function

Recipient with

type A blood

Antigen A

Left: Omikron/Science Source; Right: Lester V. Bergman/Encyclopedia/Corbis

A

B

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