Chapter 10: Immunodiagnosis Flashcards
What is serology?
The study of antibodies (Abs) and their reaction with Antigens (Ags) that bind specifically to Abs or T-cell receptors, in the diagnosis of infectious disease.
What are the advantages of immunodiagnosis?
Powerful tools for detecting infectious agents, especially those that are difficult or impossible to culture.
What are the disadvantages of immunodiagnosis?
Generally takes 10 to 14 days to produce an immune response; some longer. Immunocompromised patients may have diminished or nonexistent response. Cross-reactive Ab can yield a false-positive.
Define ‘antigen’.
Foreign compounds that stimulate immune response leading to formation of antibodies.
What are antibodies?
Proteins formed in response to stimulation by foreign antigens.
What does ‘affinity’ refer to in immunology?
Cumulative effects of forces of attraction and repulsion in antibody-antigen reaction.
Define ‘avidity’.
Sum total of all binding between antibody and antigen.
What is an epitope?
Part of antigen that binds to antibody.
What is specificity in the context of antibodies?
Ability of antibody to distinguish between antigens that have very small differences.
What is cross-reactivity?
Antibody specific for one antigen reacts with an antigen with a similar structure.
What does sensitivity mean in immunologic assays?
Ability to detect small amount of antigen or antibody.
What are polyclonal antibodies?
Contain variety of binding sites, affecting affinity and avidity. A single infecting species typically stimulates production of numerous antibodies.
Define monoclonal antibodies.
Large amounts of homogenous antibodies with high specificity and sensitivity.
What is the purpose of immunochemical methods?
To detect microorganisms through various techniques.
What is a precipitin test?
A classic test using agarose gel with wells containing serum and antibody added to adjacent wells to observe precipitin lines.
What is agglutination?
Detect Antigen/Antibody interaction.
Antigen detection markers:
Latex beads, red cells, fluorescent markers, enzyme conjugates
What are the types of agglutination?
- Direct – Natural carrier particle
- Indirect – Artificial carrier particle
- Reverse passive agglutination – antibody attached to a particle to detect an antigen.
What is latex agglutination?
A frequently used carrier molecule where each particle can hold many antibody-binding sites.
What does the Coagglutination method involve?
Antibody bound to a particle to detect soluble antigens in spinal fluid and serotyping of antigens.
What is an Enzyme-Linked Immunosorbent Assay (ELISA)?
An assay where antigen or antibody is bound to an enzyme that catalyzes a reaction, measured spectrophotometrically.
Specificity enhanced with monoclonal antibodies
What types of ELISA exist?
- Noncompetitive or sandwich
- Competitive
- Solid-phase immunosorbent assay (SPIA).
What is immunofluorescence?
A technique using fluorochrome dyes that absorb energy in ultraviolet range and convert it into light at a visible wavelength.
What does an antibody titer measure?
Measure of antibody present, reciprocal of highest serum dilution in which antibody is detected.
What is the acute phase in immunoserological applications?
Collect when disease first suspected; titer generally low.
What is the convalescent phase in immunoserological applications?
Collect while patient is recovering; titer higher.
What is required for diagnosis using paired sera?
Convalescent phase: a four-fold increase or two doubling dilutions, collected when pt is recovering
Acute: titer generally low, collected when disease first suspected
List examples of immunoserological applications.
- Precipitin Tests
- VDRL flocculation and RPR
- Direct whole particle agglutination
- Counterimmunoelectrophoresis
- ELISA
- Membrane bound ELISA
- Western Blot.
