Chapter 5: Serology Techniques

Forensic Serology The detection and measurement of

antigen-antibody binding reaction Primary binding assays Secondary binding assays

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Enzyme-Linked Immunosorbent Assays

Immunochromatographic Assays

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Most sensitive Enzyme-Linked Immunosorbent Assay

ELISA Most common method is an antibody

sandwich ELISA▪ PSA and seminal stains▪ Amylase and saliva▪ Colorimetric or fluorometric signal is

proportional to the amount of bound antigenForensic Biology by Richard Li 4

Immunochromatographic Assays Rapid and simple test Used as screening test in the field for

seminal and saliva stains and for species identification

High-dose effect

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Precipitation-based assays Based on the precipitation reaction Species identification

Immunodiffusion A passive diffusion method in which a

concentration gradient is established for an antigen and/or antibody▪ Single Immunodiffusion▪ Radial Immunodiffusion Assay

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Immunodiffusion (cont.)▪ Double Immunodiffusion▪ Gradient for both antibody and antigen▪ Ring Assay- performed in test tube or capillary tube▪ Ouchterlony Assay- Performed in an agarose gel

supported by a glass slide or polyester film

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Electrophoretic Methods Diffusion combined with electrophoresis

tp enhance results Separates molecules according to

differences in their electrophoretic mobility▪ Immunoelectrophoresis (IEP)▪ Crossed Immunoelectrophoresis (CRIE)▪ Rocket Immunoelectrophoresis▪ Crossover Immunoelectrophoresis

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Agglutination-based Assays Used for blood group typing and species

identification Simple, more sensitive than precipitation

techniques Identify antigen or antibody

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Agglutination-based Assays (cont.) Direct agglutination assay▪ Antibody interacts with the antigens originally

located on the cell surface▪ Hemmagglutination reaction

Passive agglutination assay▪ Employ coated erythrocytes▪ Species identification

Agglutination inhibition assay▪ Indirect way to identify the antigen in question

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