Ch 11: labeled immunoassays

  1. what is the purpose of labeled immunoassays
    to detect antigens and antibodies that may be mall in size or present in very low concentrations using a labeled reactant to monitor the specific antigen-antibody binding
  2. what is the process for competitive immunoassays
    • all reactants are mixed together simultaneously
    • labeled antigen competes with unlabeled patient antigen for a limited number of antibody binding sites
    • the amount of bound label is inversely proportional to the concentration of the labeled antigen
  3. Image Upload 1
    competitive immunoassays
  4. describe process of noncompetitive immunoassays
    • antibody is anchored and absorbed into a solid phase
    • unknown patient antigen is reacted an captured by antibody
    • Solid is washed to remove unbound antigen and an anti antibody with label is added to the reaction
  5. noncompetitive immunoassays concentration of labelled and unlabelled antibody
    the amount of label measured is directy proportional to the amount of patient antigen
  6. Image Upload 2
    non competitive immunoassay
  7. theory behind Enzyme immunoassays (EIAs or ELISA)
    using enzymes as labels which react with substrates to produce breakdown product that may be fluorogenic, luminescent, or chromogenic
  8. what is the most commonly used enzyme label
    • alkaline phosphatase
    • horseradish peroxidase
    • both have high sensitivity and easy to detect

    highest conversion of substrate rates (turnover)
  9. what are ELISAs used for
    • HIV
    • hepatitis B
  10. ELISAs produce a sandwhich immunoassays because
    • antigens that have multiple determinants such as 
    • antibodies
    • cytokines
    • tumor markers
  11. heterogeneous ELISA or homogeneous ELISA require washing step
  12. which is more sensitive
    heterogenous assay or homogenous assay
    heterogenous assay
  13. homogenous EIAs
    • do not require a washing step
    • enzyme activity is proportional to concentration of patient antigen present
  14. fluorescent immunoassays are restricted in what way
    qualitative observations using a fluorescent microscope
  15. fluorescent immunoassays are used for
    • identification of microorgansism in cell culture or infected tissue, neoplastic tissue
    • used to determine concentration of therapeutic drugs
  16. described the theory of chemiluminescent immunoassays
    • involves the emission of light caused by oxidation reaction producing an excited molecule as it decays back to its original ground state
    • can be used for heterogeneous and homogeneous assays because labels can be attached to either antigen/ antibody.
Card Set
Ch 11: labeled immunoassays
immunoassays and labeling