Forensic Serology
What is Blood?
Blood is a highly complex mixture of
 cells
 enzymes
 proteins
 inorganic substances.
What is Blood?
Fluid portion of blood is called plasma.
Plasma is composed mainly of water and
 electrolytes
 nutrients
 vitamins
 hormones
 clotting factors
 proteins such as antibodies to fight infection.
Accounts for 55% of blood content.
What is Blood?
Suspended in the plasma are solid materials,
chiefly:
 Red blood cells
 White blood cells
 Platelets
The solid portion of blood accounts for 45%
of its content.
What is Blood?
Red Blood Cells (RBC) - Erythrocytes
 The most abundant cells in our blood;
 They are produced in the bone marrow
 They contain a protein called hemoglobin
that carries oxygen to our cells.
Red Blood Cell Journey
What is Blood?
White Blood Cells (WBC) - Leukocytes
 They are part of the immune system
 They destroy infectious agents called
pathogens.
 Short video of a white blood cell chasing bacteria (no sound)
What is Blood?
PLATELETS (Thrombocytes) –
 The clotting factors that are carried in the plasma;
 They clot together in a process called coagulation
to seal a wound and prevent a loss of blood.
Serum
The liquid that separates from the blood when a
clot is formed. (pale yellowish color)
What is Blood?
Review
Antigens
Blood Typing
 Are usually a protein that stimulates the
body to produce antibodies against it.
 Have nothing to do with oxygen
transport
 Antigens with common traits are
grouped into systems.
Antigens
Blood Typing
 15 different systems have been identified.
 Most important system is A-B-O
Blood Typing
 There are 3 alleles
or genes for blood
type: A, B, & O.
 Since we have 2
genes, there are 6
possible
combinations.
Blood Typing
 Notice Type A blood only
contains B antibodies (or
Anti-B) in the plasma.
 When Type A blood
encounters A antibodies,
agglutination will occur.
 Agglutination = clumping
 Type AB contains neither
antibody and Type O
contains both.
Blood Typing
The third antigen observed in the A-B-O
system is the Rh antigen. Also known as:
 Rh Factor
 D antigen
 The presence of the Rh antigen found on a
red blood cell would mean that the blood is
Rh +.
Blood Typing
Population distribution
of blood type varies
with location and race
throughout the world.
According to your text:
O = 43%
A = 42 %
B = 12%
AB = 3%
Which is the most
common?
Blood Typing - continued
Serum is the part of the plasma that contains the
antibodies.
The Fundamental Principle of Blood Typing:
 For every antigen there is a specific antibody that
will react with it to form clumps known as
agglutination.
 Thus, if serum containing anti-B is added to red
blood cells carrying B antigen, they will
immediately react – meaning clumps will form.
(Thus the blood will be Type B)
Blood Typing - Continued
Blood Transfusions - is a procedure in which blood
is given to a patient through an intravenous (IV) line
in one of the blood vessels.
What could happen if a person
receives blood that is incompatible?
Agglutination or clumping = death
 Type O = universal donors
 Type AB = universal receivers
 Rh +  Can receive + or -
 Rh -  Can only receive -
Blood Typing Game
 http://www.nobelprize.org/educational/medicine/landstei
ner/index.html
Actual Blood Typing Demo