Chapter 10 Forensic Serology * * Antigens * Antigens

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Chapter 10Forensic Serology
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All About Blood
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Nature of Blood

• Highly complex mixture
• Cells
• Enzymes
• Proteins
• Inorganic substances
• Plasma
• Fluid portion of blood
• Principally of water

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Formed Elements

• Red blood cells (erythrocytes)
• White blood cells (leukocytes)
• Platelets
• Suspended in plasma

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Formed Elements
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Formed Elements
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Formed Elements
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Formed Elements
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Formed Elements
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Formed Elements
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Blood Typing
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Blood Typing

• Antigens
• Surface of red blood cells
• Responsible for blood-type characteristics
• More than 15 blood antigen systems identified
• ABO, Rh systems most important

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Blood Typing ABO Blood Groups

• Type A ? A antigens on red blood cells
• Type B ?B antigens
• Type AB ?both A and B antigens
• Type O ? neither A nor B antigens

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Blood Typing Rh Factor

• D antigen
• Presence of D antigen ? Rh positive
• No antigen ? Rh negative

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Blood Typing Hemagglutination

• Specific antibody reacts to form clumps
• Natural antibodies in blood to ABO antigens
• Serum containing anti-B is added to red blood
  cells carrying B antigen ? immediately reaction

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Red Cell Agglutination
Figure 121  
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ABO Reactions
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Serology

• Specific antigen and serum antibody reactions
• Identity four ABO blood groups
• Test blood with anti-A and anti-B sera
• Applied to immunoassay techniques for detection
  of drugs of abuse in blood and urine

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EMIT

• Enzyme-multiplied immunoassay technique
• Speed
• High sensitivity
• Detects drugs in urine
• Antibodies bind to specific drug added to the
  subjects urine

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EMIT

• Drug combines with AB
• Enzyme-labeled drug added
• Unreacted AB combine with labeled drug
• Uncombined enzyme-labeled drug measured by enzyme
  reaction

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Other Immunoassay Procedures

• Radioimmunoassay (RIA)
• Drugs
• Labeled with radioactive tags

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Antigen-Antibody Reaction

• Animal injected with an antigen
• Body produces different antibodies
• All will attack some particular site on the
  antigen of interest
• Collection of antibodies is known as polyclonal
  antibodies

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Polyclonal AB Production
Figure 123  

• Drug molecule too small to induce AB production
• Carrier protein needed

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Hybridomas Monoclonals

• Antibodies designed to combine with a single
  antigen site
• Myeloma cells
• Spleen cells
• Commercial applications

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Forensics of Blood
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Forensics of Blood

• Examination of dried blood
• Blood?
• Species of origin?
• If human origin, associated to a particular
  individual?
• Preliminary color test

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What is this stain?
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Kastle-Meyer Color Test
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• Indicative of blood
• Hemoglobin causes deep pink color

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Kastle-Meyer Color Test
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Luminol Test

• Trace amounts of blood located at crime scenes
• Produces light (luminescence) in a darkened area

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Microcrystalline Tests

• Takayama and Teichmann tests
• Small amount of blood added to microscope slide
• Chemical solution added
• Slide heated to form hemoglobin crystals (a pink
  crystal complex)
• Crystals can be viewed under a microscope
• Positive results indicate blood
• Sensitivity 0.001 ml of blood/0.1 mg hemoglobin
• 20 year old blood stains have given positive
  results

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Antigens Antibodies
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Antigens
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Antigens

• Chemical characteristics
• Proteins
• Larger than 10,000 mw
• Epitopes or antigenic determinants
• Multivalent antigen
• Multiple binding site for different ABs
• Each binding site induces different AB

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Immunoglobulin

• Blood protein
• Antigen binding sites
• Specific for AG that induced formation
• Complex genetics determination

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Specificity Of Antibodies

• Clonal selection theory
• Burnet, Talmage and Jerne

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The Primary Secondary Antibody Response
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The Tests Human or Animal

• Antisera
• Derived from rabbits
• Injected with the blood of known animal
• Determines species origin of questioned
  bloodstain
• Precipitin test

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Test for Human Blood
Figure 126  
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Immune Complex Formation
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Ouchterlony Test
Figure 127  
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Ochterlony Plate
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ABO vs DNA

• ID stain to one individual
• Prior to DNA typing
• ABO typing
• Polymorphic blood enzymes and proteins
• Supplanted by the newer DNA technology

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DNA analysis

• Associate blood and semen stains to a single
  individual
• Transmission of hereditary material
• Genes
• Located on chromosomes
• Alleles
• Alternative forms of genes
• Influence a given characteristic (such as eye
  color or blood type)

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Heredity and Paternity

• Historically
• ABO blood typing system
• Plus blood factors other than ABO
• Currently
• DNA test procedures
• Odds of establishing paternity beyond 99 percent

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ABO Reactions
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Testing for Seminal Stains

• Sexual offenses
• Necessary to examine exhibits for the presence of
  seminal stains
• Acid phosphatase
• An enzyme secreted into seminal fluid
• Locate
• Purple color indicates acid phosphatase enzyme
• Unequivocally identification
• Spermatozoa
• p30 protein unique to seminal plasma
• Link to individual by DNA typing

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Immunology-Anti-p30

• Identification of semen in aged evidence samples
  possible
• Prostate specific antigen (PSA, also known as
  p30)
• Glycoprotein produced by prostate gland
• Secreted into seminal plasma (fluid)
• Concentrations of  200,000 to 5.5 million ng/ ml
• Confirms the presence of semen even in samples
  that involve vasectomized or azospermic
  individuals

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ELISA Method
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ELISA Test for PSA
Figure 1220  An antibodyantigenantibody
sandwich or complex is seen as a colored band.
This signifies the presence of PSA in the extract
of a stain and positively identifies human semen.
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ELISA Plate
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Rape Evidence

• Medical examination as soon as possible after the
  assault
• Collection of physical evidence
• Clothing
• Hairs
• Vaginal and rectal swabs
• All outer and undergarments
• Carefully removed
• Packaged separately
• Paper (not plastic) bags
• Bedding, or the object upon which the assault
  took place

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Rape Evidence

• If suspect is apprehended within 24 hours of The
  assault
• Possible to detect the victims DNA
• Males underwear
• Penile swab of the suspect
• Items routinely collected from the suspect
• All clothing
• Pubic hair
• Head hair
• Penile swab
• Blood sample or buccal swab for DNA typing.
• May result in transfer of such physical evidence

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Summary