1 / 22

Immunologic Methods

CLS 420 Clinical Immunology & Molecular Diagnostics. Immunologic Methods. Part One Antigen-Antibody Reactions. Objectives. Discuss the following as related to immunology testing: Equivalence zone Postzone Prozone Sensitivity Specificity Cross-reactivity Screening test

lillian-daugherty
Download Presentation

Immunologic Methods

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CLS 420 Clinical Immunology & Molecular Diagnostics Immunologic Methods Part One Antigen-Antibody Reactions

  2. Objectives • Discuss the following as related to immunology testing: • Equivalence zone • Postzone • Prozone • Sensitivity • Specificity • Cross-reactivity • Screening test • Confirmatory test

  3. Objectives • Explain how the following physical factors can affect antigen-antibody reactions: • Ionic strength • pH • Reaction time • Temperature • Concentration ratio of antigen and antibody

  4. The study of host reactions to foreign substances. The study of serum; in particular, the study of antibodies in serum and other body fluids. Immunology vs. Serology

  5. Sensitivity & Specificity • Sensitivity: How well a test is able to detect minute quantities of an analyte. • Specificity: The ability of a test to detect one unique analyte.

  6. Cross Reactivity • Reactions with substances that are structurally similar to an analyte.

  7. Predictive Value • The probability that a laboratory test result will correctly diagnose or rule out a particular disease. • Predictive Value - Positive is the probability that a positive test result is associated with disease. • # of true positives / (# of true positives + # of false positives) • Predictive Value - Negative is the probability that a normal test result is not associated with disease. • # of true negatives / (# of true negatives + # of false negatives) Cut-off value “Normal”Disease # of patients Test Result Value

  8. Screen vs. Confirm • Screening Test: A test used to detect disease, usually in someone who is asymptomatic. They are highly sensitive but are not as specific as the confirmatory tests. • Confirmatory Test: Highly specific tests that are run to validate the results of the initial screening test.

  9. Antigen/ Antibody Reactions

  10. Antigen / Antibody Binding • Antigen and antibody bind with “Lock and Key” fit. • Affinity – the total attractive force that draws antibody to antigen. • Avidity – how “tightly” antigen and antibody bind. AG AB

  11. Equilibrium • Antigen / antibody reactions are readily reversible. • Free Ag + Free Ab Ag-Ab complex

  12. Antigen / Antibody Reactions • May be visualized when lattice structures form. • Sensitization • Agglutination or precipitation Y Y Y Y Y Y

  13. Zone of Equivalence Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Postzone-antigen excess Prozone – antibody excess

  14. Antigen/antibody reactions are influenced by:

  15. Ionic Strength • Shielding – charges that surround the Fab portion of an antibody, blocking antigen/antibody binding • Zeta potential – the difference in electrical charge between the surface of a cell and the outer layer of the ionic cloud that surrounds the cell in an electrolyte solution. • Keeps cells too far apart to allow lattice formation

  16. Zeta Potential Y Y Y Y - - - - - - - - - - - - - - ++++++++++++++ Y Y J - - - - - - - - - - - - - ++++++++++++++ - - - - - - - - - - - - - - -

  17. Ag/Ab binding is influenced by: • pH • Reaction time • Temperature • Number of antigens

  18. Dosage • Antibodies that react stronger with cells that have homozygous expression of an antigen than they do with cells that have heterozygous expression are said to show dosage • Cells with homozygous antigen expression have twice as much antigen available to participate in the reaction than do cells with heterozygous antigen expression

  19. If there is an anti- antibody, which of these cells will yield the stronger reaction with it? Homozygous Heterozygous

  20. Location of Antigens • Free antigens and cell surface antigens are more available to react than those buried within the membrane or within the cell. • Interference in ag/ab binding due to the position of other antigens Y Y Y Y

  21. Concentration Ratio of Ag/Ab Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Postzone-antigen excess Prozone – antibody excess Zone of Equivalence

  22. The End Specific, basic immunologic methods are discussed in the PowerPoint, “Immunologic Methods, Part 2”.

More Related