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Chapter 12 - PowerPoint PPT Presentation

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Chapter 12

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  1. Chapter 12 Forensic Serology

  2. What is serology? • A range of laboratory tests using antigens and antibodies Antibody

  3. Antigens are cell membrane proteins

  4. Blood • Cells • Red blood cells (RBCs, erythrocytes) • White blood cells (WBCs, leukocytes) • Platelets • Proteins • Enzymes • Plasma (watery fluid)

  5. Red blood cells • Antigen systems • A-B-O • Rh factor

  6. Blood serum • Antibodies • Proteins which bind to specific antigens • Antiserum – serum containing Ab(s) that react against (bind to) specific antigens • Agglutination – clumping of RBCs by reaction (binding) to antibodies

  7. Blood type, antigens and serum

  8. Serology • Blood typing • Identifying A-B-O type with known antiserum (by agglutination) • Identifying A-B-O type with known RBCs (by agglutination)

  9. Serology • Immunoassays • EMIT (Enzyme-multiplied immunoassay technique) • RIA (Radioimmunoassay) • Mabs (monoclonal antibodies)

  10. EMIT • An exactly known amount of the enzyme-labeled conjugate (drug, for example) is then added to the mixture at which point, binding sites on the antibody not occupied by drug molecules become filled with enzyme-labeled drug molecules. Only unbound enzyme conjugate is active so that conversion of colorless NAD+ to the colored NADH is indicative of the amount of free enzyme conjugate and, therefore, drug in the analytical sample

  11. Radioimmunoassay • Detect amount of radioactivity

  12. Mabs

  13. Forensic analysis of bloodstains • Blood or not blood • Species identification • Association with an individual

  14. Identifying a stain as blood • Kastle-Meyer color test • Hemoglobin acts like a peroxidase • Hemastix® • Luminol test

  15. Identifying blood as human • Precipitin test • Uses species-specific antiserum • Excellent sensitivity • Can be used on old blood samples

  16. Precipitin test • Gel diffusion • Gel electrophoresis

  17. Association of blood with an individual • Historical methods • A-B-O typing • Isozyme analysis • Polymorphic enzymes

  18. Association of blood with an individual • Modern method • DNA profiling/typing

  19. Paternity testing and serology • Historical method • A-B-O typing • HLA (Human leukocyte antigen) test • Modern method • DNA profiling/typing

  20. Serology & semen • Acid phosphatase color test • p30 or PSA (prostate specific antigen) immunoassays

  21. Serology & semen