FRSC 1010H Chapter Notes - Chapter 15: Red Blood Cell, Karl Landsteiner, Urine Test Strip
3 May 2018
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Chapter 15: Biological Stain Analysis
● Karl Landsteiner announced one of the most significant discoveries of the
twentieth century, the typing of blood and finding this earned him a Nobel Prize.
● Landsteiner was the first to recognize the all human blood was not the same.
● Until the early 1990’s forensic scientists focused on blood factors, such as A,B,O,
as offering the best means of linking blood to individuals.
● Today the high sensitivity of DNA analysis and the resultant search for DNA
evidence has even altered the types of materials collected from crime scenes.
● Deoxyribonucleic Acid (DNA)
○ The molecules that carry the body’s genetic information.
● The word “blood” refers to a highly complex mixture of cells, enzymes, proteins,
and inorganic substance.
● The fluid portion of the blood is called plasma; it is composed principally of water
and accounts for 55% of blood content. The solid portion of blood accounts for
45% of its content.
● Plasma;
○ The fluid portion of unclotted blood.
● Suspended in the plasma are solid materials of cells: red blood cells
(erythrocytes), white blood cells (leukocytes) and platelets.
● Blood clots when a protein in the plasma known as “fibrin” traps and enmeshes
the red blood cells.
● If the clotted material were removed from the blood, a pale yellowish liquid known
as serum would be left.
● Serum
○ The liquid that separates from the blood when a clot is formed.
● Red blood cells transport oxygen and remove carbon dioxide from tissues. On
the surface of each cell are millions of characteristic chemical structures called
antigens.
● Antigens
○ A substance, usually a protein, that stimulates the body to produce
antibodies against it.
● More than fifteen blood antigen systems have been identified to date; of these,
the A-B-O and Rh systems are the most important.
● If an individual has type A blood, this simply means that each red blood cell has
A antigens on its surface; similarly, all types B individuals contain both A and B
antigens. Type o individuals have neither A nor B antigens on their cells.
● Another important blood antigens has been named the “Rh factor” or D antigen.
Those people who have the D antigens are said to have “Rh positive”; those
without this antigens are “Rh negative”.
● Serum is important because it contains proteins known as antibodies.
● Antibody
○ A protein in the blood serum that destroys or inactivates a specific antigen.
● For every antigen, there exists a specific antibody
● Each antibody symbol contains the prefix “anti-”, followed by the name of the
antigen for which is specific. ( anti-A only for A antigen, anti-B only for B antigen.)
● The antibody-containing serum is referred to as the antiserum.
● Antiserum
○ Blood serum that contains specific antibodies
● An antibody reacts only with its specific antigen and no other
● Antibodies are normally bivalent that is, they have two reaction sites, this means
that each antibody can simultaneously be attached to antigens located on two
different red blood cells. This creates a vast network of cross-linked cells usually
seen in the form of clumping, or agglutination.
● Agglutination
○ The clumping together of red blood cells by the action of an antibody.
● In normal blood antigens on red blood cells and antibodies coexist without
destroying each other because the antibodies present are not specific toward any
of the antigens.
● If a foreign serum is added to the blood introduces a new antibody. This results in
a specific antigen-antibody reaction that immediately causes the red blood cells
to link together, or agglutinate.
Blood Type
Antigens on Red Blood
Cells
Antibodies in Serum
A
A
Anti-B
B
B
Anti-A
AB
AB
Neither anti-A nor anti-B
O
Neither A nor B
Both anti-A and anti-B
● Fatal consequences for mixing incompatible blood.
○ The transfusion of type A blood into a type B patient will cause the natural
anti-A in the blood of the type B patient to react promptly with the incoming
A antigens, resulting in agglutination. In addition, the incoming anti-B of
the donor will react with the B antigens of the patient.
● The concept of a specific antigen-antibody reaction is being applied in other
areas like detection of drugs in blood and urine.
● Antibodies that react with drugs do not exist naturally (but can be produced by
some animals like rabbits).
● This drug-protein complex acts as an antigen, stimulation the animal to produce
antibodies. The recovered blood serum of the animal now contains antibodies
that are specific or nearly specific to the drug.
● Immunoassay testing for drugs has proved quite suitable for handling the large
volume of specimens that must be rapidly analyzed on a daily basis for drug
content. Once a particular serum is added to a urine specimen, it’s designed to
interact with either opiate, cannabinoids, amphetamines, phencyclidine,
barbiturates, methadone, or another type of drug that might be present.
● Caution: Immunoassay is only presumptive in nature, and its result must be
confirmed by additional testing.
● Quick Review
○ An antibody reacts or agglutinates only with its specific antigen. The
concept of specific antigen-antibody reactions has been applied to
techniques for the detection of commonly abused drugs in blood and
urine.
○ Every red blood cell contains either an A antigen, a B antigen, both
antigens, or no antigen (this is called “type O”). This type of antigen on
one’s red blood cells determines one’s A-B-O blood type. Persons with
type A blood have A antigens on their red blood cells, those with type B
blood have B antigens, those with type AB blood have both antigens,and
those with type O blood have no antigens on their red blood cells.
○ To produce antibodies capable of reacting with drugs, a specific drug is
combined with a protein, and this combination is injected into an animal
such as a rabbit. This drug-protein complex acts as an antigen, stimulating
the animal to produce antibodies. The recovered blood serum of the
animal will not contain antibodies that are specific or nearly specific to the
drug.
● The criminalist must answer these questions when examining dried blood:
○ Is it blood
○ From what species did the blood originate
○ If the blood is human, how closely can it be associated with a particular
individual
● The determination that a substance is blood is best made by means of
preliminary colour testing. Before that the most common test was the ‘Benzidine
color test”
Document Summary
Karl landsteiner announced one of the most significant discoveries of the twentieth century, the typing of blood and finding this earned him a nobel prize. Landsteiner was the first to recognize the all human blood was not the same. Until the early 1990"s forensic scientists focused on blood factors, such as a,b,o, as offering the best means of linking blood to individuals. Today the high sensitivity of dna analysis and the resultant search for dna. Deoxyribonucleic acid (dna) evidence has even altered the types of materials collected from crime scenes. The molecules that carry the body"s genetic information. The word blood refers to a highly complex mixture of cells, enzymes, proteins, and inorganic substance. The fluid portion of the blood is called plasma ; it is composed principally of water and accounts for 55% of blood content. Suspended in the plasma are solid materials of cells: red blood cells (erythrocytes), white blood cells (leukocytes) and platelets.
