Chapter 5: Serology Techniques

 Forensic Serology  The detection and measurement of antigen- antibody binding reaction  Primary binding assays  Secondary binding assays Forensic Biology by Richard Li2

 Enzyme-Linked Immunosorbent Assays  Immunochromatographic Assays Forensic Biology by Richard Li3

 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 antigen Forensic Biology by Richard Li4

 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 Forensic Biology by Richard Li5

 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 Forensic Biology by Richard Li6

 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 Forensic Biology by Richard Li7

 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 Forensic Biology by Richard Li8

 Agglutination-based Assays  Used for blood group typing and species identification  Simple, more sensitive than precipitation techniques  Identify antigen or antibody Forensic Biology by Richard Li9

 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 Forensic Biology by Richard Li10