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IMMUNITY AND ELISA

IMMUNITY AND ELISA. IMMUNOLOGY. Study of the immune system How the body protects itself against foreign, potentially disease-causing microorganisms Three main functions: To recognize intruders To respond appropriately to intruders in a way that protects the body

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IMMUNITY AND ELISA

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  1. IMMUNITY AND ELISA

  2. IMMUNOLOGY • Study of the immune system • How the body protects itself against foreign, potentially disease-causing microorganisms • Three main functions: • To recognize intruders • To respond appropriately to intruders in a way that protects the body • To respond the next time the intruders are encountered

  3. IMMUNITY • Innate immunity • Nonspecific • Adaptive Immunity • Specific • Induced resistance to a specific pathogen • Humoral versus cell-mediated • B cells versus T cells

  4. ANTIGENS • A substance that causes the body to produce specific antibodies or sensitized T cells • Protein or polysaccharide (lipids and nucleic acids when combined with proteins or polysaccharides) • Found in capsule, cell walls, flagella, fimbrae, and toxins of microbes • Pollen, egg white, blood cell surface, tissue surface • Antigenic determinants (epitopes) • Specificity • Each bacterial cell has many different epitopes

  5. Figure 17.1

  6. ANTIBODIES • Globular proteins (immunoglobulins) made by B cells in response to an antigen • Highly specific • Antigen-binding sites

  7. Human Immunodeficiency virus (HIV) • First diagnosed in 1981 • Over 20 million deaths worldwide, over a half million in the United States • Over 40 million currently infected, over a million in the United States • Half of all new infections are in people younger than 25 • Education has been effective in limiting the spread of HIV/AIDS

  8. Human Immunodeficiency virus (HIV) • HIV is an RNA Retrovirus • Transmitted by exchange of body fluids, sharing needles, or blood transfusion • Infects T-Cells in the immune system and thus destroys the immune system • Flu-like symptoms within 1-2 months followed by latent period of up to 10 years • HIV may have spread from an animal host to humans • Treated but not cured by drugs which inhibit the action of HIV enzymes • High error rate of replication (1/2000 nucleotides)

  9. Schematic of HIV Virion Figure 16-11b

  10. Diagnostic Immunology • Diagnostic techniques help us determine the etiology of the disease • Diagnostic techniques • Microscopy • Culture • Test biochemical properties of microbe • Molecular • Use PCR to amplify a gene associated with the disease • Identify the gene on a gel • Immunological

  11. Diagnostic Immunology • Diagnostic immunology involves using the principles of the immune system or antibody—antigen reaction to diagnose diseases or detect antigens in bodily fluids • Important diagnostic tests • Direct agglutination • Indirect agglutination • Hemagglutination • ELISA

  12. Principles of Diagnostic Immunology • Physician collects a sample • Antigen sample • A bodily fluid that contains the infecting microbe or the microbes toxin • Urine, feces, blood, skin, pus, throat swab, mucous, etc. • Blood antiserum sample • Blood antiserum contains the antibodies that the patient made against an infection; if the patient is infected with the suspected pathogen then his/her serum has those antibodies in it.

  13. Principles of Diagnostic Immunology • If the sample is… • Antigen then the physician exposes it to pre-made antibodies for the suspected pathogen • Antibodies are produced by a rabbit that was infected with that organism; they are collected in sterile vials and sold by pharmaceutical companies • Blood antiserum then physician exposes it to an antigen from the suspected pathogen • Antigen from microorganism is prepared by pharmaceutical company • It could be a toxin, an inactivated whole agent, or any subunit from the suspected pathogen

  14. Viral serology • Enzyme Linked Immunosorbent Assay (ELISA) • Initial diagnostic test used for HIV detection • Done on women in labor before delivery to determine infection status • Patients following an accidental needlestick injury • Enzyme reacts with substrate to produce colored product • Very sensitive • How ELISA works • Microplates • Made of polystyrene which binds proteins by hydrophobic interaction. • Primary and secondary antibodies • Color producing enzyme substrate

  15. ELISA Procedures Modified from Specter, S. C., R. L. Hodinka and S. A. Young. Clinical Virology Manual, Third Edition . ASM Press, 2000.

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