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Forensic Serology
Objectives:
1.
Identify and describe the components of human blood
2.
List the A-B-O antigens and antibodies found in the blood for each
of the four blood types: A, B, AB, and O.
3.
Explain why agglutination occurs.
4.
Explain how whole blood is typed.
5.
Describe tests used to characterize a stain as blood.
6.
Explain the significance of the precipitin test to forensic serology.
7.
Explain the differences between monoclonal and polyclonal
antibodies.
8.
Define chromosome and gene.
9.
How is the Punnet square used to determine the genotypes and
phenotypes of offspring?
10. List the laboratory tests necessary to characterize seminal stains.
11. Explain how suspect stains are to be properly preserved for
laboratory examination.
12. Describe the collection of physical evidence related to a rape
investigation.
5/23/2017
Created by C. Ippolito
January 2008
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Blood
• complex mixture of cells and fluid
• Formed Elements
– living component
– cells suspended in the liquid
• Plasma
– nonliving fluid matrix of unclotted blood
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Created by C. Ippolito
January 2008
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Plasma
• 55% of whole blood
• 90% water
• 10% dissolved components
– nutrients
• sugars, lipids (fats), amino acids
– gases
• CO2 (bicarbonate ion HCO3-)
– salts
• ionic compounds containing (Na+, K+, Mg2+, Cl-)
– hormones
– plasma proteins
• albumen – maintains osmotic pressure, pH buffering
• globulins - antibodies – protective proteins of immune response
• fibrinogen – protein that contributes to blood clotting mechanism
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Formed Elements
• 45% of whole blood
• Three main blood cell types
– Erythrocytes (RBC)
• transport O2
– Leukocytes (WBC)
• disease defense
– Thrombocytes (platelets)
• clotting mechanism
• cell pieces
– initiate clotting
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Created by C. Ippolito
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Erythrocytes
• most numerous blood cells
– anucleate – no nucleus
– hemoglobin (Hb)
• iron containing protein
• transports O2
– biconcave disk
• increases surface area
– membrane antigens
• determine blood types
• Anemia
– lack of RBC
• Polycythemia
– excess RBC
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Created by C. Ippolito
January 2008
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Leukocytes
• less numerous blood cells
• defense against
– bacteria, viruses, parasites,
tumor cells
• Leukocytosis
– high WBC count
– indicative of infection
• Leukopenia
– low WBC count
– corticosteroid use, certain
drugs, anticancer agents
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Types of Leukocytes
• Neutrophils
– phagocytes – “eating cells”
• attack in acute (short-term) infections
• Eosinophils
– attack parasitic worms
– numerous during allergies
• Basophils
– release histamine
• vasodilator releases plasma and WBC at
infection site
• Lymphocytes
– B-cells – release antibodies
– T-cells – attack viruses and tumors, activate
B-cells
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Created by C. Ippolito
January 2008
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Human Blood Groups
• RBC antigens
– antigen
• identifying protein that is genetically determined
• recognized by a “body” as being foreign
– antibody
• protein released by B-cells
• “match” antigens’ shape
• minimum of 2 active sites (bivalent)
• Agglutination
– antibodies attach to RBC antigens
– RBC interconnect through antibodies
– RBC clump together clogging BV
• Serum
– plasma with antibodies
5/23/2017
Created by C. Ippolito
January 2008
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RBC Agglutination
• RBC
membrane
antigen
• Antibody
matches
and
attaches to
multiple
RBCs
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Created by C. Ippolito
January 2008
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ABO Blood Typing
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Created by C. Ippolito
January 2008
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Type AB Blood
• RBC has both antigens A and B
– reacts with anti-A serum
– reacts with anti-B serum
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Type A Blood
• RBC has only antigen A
– reacts with anti-A serum only
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Type B Blood
• RBC has only antigen A
– reacts with anti-B serum only
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Type O Blood
• RBC has no antigen
– no reaction with anti-A serum
– no reaction with anti-B serum
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Created by C. Ippolito
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Blood Type Distribution
• In the US a “typical” ABO distribution is as
follows:
– 43% type O
– 42% type A
– 12% type B
– 3% type AB
• ABO Blood Type distributions
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Created by C. Ippolito
January 2008
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Immunoassay
• Using antibody-antigen reactions to identify
substances
– original pregnancy tests (clotting to HCG)
– use rabbits to make antibodies to react with drugs
– antibodies (sera) then used in urinalysis
• opiates, cannabinoids, cocaine, amphetamines,
phencyclidine, barbiturates, methadone can be identified,
• presumptive testing, results must be confirmed
by additional tests
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Created by C. Ippolito
January 2008
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Radioimmunoassay (RIA)
• uses drugs labeled with radioactive tags
– can react with substances chemically similar
to target substance
– also needs confirmation
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EMIT
• Enzyme-Multiplied Immunoassay Technique
–
–
–
–
add antibodies to urine for particular drug
add chemically labeled version of presumed drug
competition between labeled and unlabeled
amount of labeled drug left in test related to amount
of original drug in sample
• labeled drug left over means original drug combined with
antibodies and was removed
• used to test for THC (tetrahydrocannabinol) and
it metabolites such as THC-9-carboxylic acid
– shows marijuana use but can yield positive results for
up to 10 days after last use
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Created by C. Ippolito
January 2008
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Polyclonal and Monoclonal
Antibodies
• Polyclonal antibodies
– multiple antibodies produced to attack many different parts of a
single antigen
• preferable in immune response against a disease organism
• Monoclonal antibodies
– single antibody produced to attack a specific part of a specific
antigen
• preferable in an “assay” test to identify one particular substance
– hybridoma cells
• mouse spleen cells and blood cancer cells combine producing a
single antibody
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Created by C. Ippolito
January 2008
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Forensic Characterization of Blood
Stains
• Three questions must be answered:
– Is it blood?
• Color Tests
• Luminol Test
• Microcrystalline Test
– Is it human blood?
• Precipitin Test
• Gel Diffusion Test
– Can it be associated with a particular person?
• ABO typing (rarely done)
• DNA profiling
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Created by C. Ippolito
January 2008
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Color Tests
• Hemoglobin – acts like peroxidase
– enzyme accelerates oxidation in presence of
hydrogen peroxide causing a color change
• enzyme also found in potatoes and horse radish
– pink color indicates presence of hemoglobin
• Benzidine Test
– discontinued as a carcinogen
• Kastle-Meyer Test
– uses phenolphthalein
• Hemastix
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– dipstick test for blood in urine
– used as presumptive blood test when moistened with distilled
water
– turns green when in contact with blood
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Luminol Test
• Luminol
– luminol + hydrogen
peroxide  3aminophthalate
• luminescence rxn
• chemical produces blue light
– does not affect subsequent
DNA testing
5/23/2017
Created by C. Ippolito
January 2008
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Microcrystalline Tests
• addition of chemicals causes hemoglobin
to crystallize
– susceptible to contaminants giving false
positives
• Takayama Test
• Teichmann Test
• Wagenhaar test
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Created by C. Ippolito
January 2008
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Precipitin Tests
• Human antiserum
– derived from animal
antibodies produced in
response to exposure
to human blood
• rabbits, cat, dogs, deer
used as sources
– reaction of antigenantibody forms cloudy
ring where they meet in
capillary/test tube
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Created by C. Ippolito
January 2008
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Gel Diffusion Test
• antigen-antibody reaction
– coagulate when meet
– very sensitive
– works with dried blood stains after 15
years
– can be diluted to 1/256 and still react
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Created by C. Ippolito
January 2008
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