Immunodiagnosis Flashcards
what are serological applications?
the use of antibodies or antigens as reagents where antibodies are used to detect antigens and antigens are used to detect antibodies
what are agglutination tests?
- agglutination is clumping of particulate antigens (e.g., cells, bacteria, or latex beads) when they react with specific antibodies
what is indirect or passive agglutination?
coating antigen on the surface of a carrier molecule - used to detect antibodies - when the antibody binds to the coated antigen, agglutination takes place on the surface of the carrier.
what is reverse passive agglutination?
antibody is coated on a carrier molecule that detects antigen in the patient’s serum.
what is a Hemagglutination Assay?
used to detect and measure antibodies or viruses that cause agglutination (clumping) of red blood cells (RBCs)
- Highest dilution of serum that still causes agglutination
what is the prozone of an Agglutination test?
Antigen is completely covered with antibody molecules (too many) hence cannot cross-link
what is an example of an Agglutination test?
test for rheumatoid factor
how do you test for Rheumatoid factor?
- reagent: human IgG latex particles
- Rheumatoid factor: an IgM in Rheumatoid arthritis that auto reacts with human IgG
what can be used to avoid false positives in prozone of agglutination tests?
secondary antibodies
what are limitations of agglutination tests?
- positive result does not necessarily mean the patient is sick ( they may have had the disease and recovered)
- false negatives: poor producers of antibodies
- false positives: a positive result may occur if an unrelated antibody reacts with the antigen non-specifically
what are precipitation tests?
- precipitation tests occurs when soluble antigens react with specific antibodies to form visible, insoluble complexes (precipitates)
what are the three zones of precipitation tests?
- Antibody excess zone: Not enough antigen molecules for cross-linking to form a stable complex - no precipitation
- Equivalent zone: The antigen-antibody ratio is in good proportion for cross-linking to form large aggregates- precipitation.
- Antigen excess zone: Each molecule of antibody is saturated with antigen, insufficient cross-linking - no precipitation
how are quantitative precipitation curves derived?
experiments where increasing amounts of antigen are added to a fixed amount of antibody
what are the Ouchterlony immunodiffusion tests commonly used for?
identifying antigenic relationships
what do lines of identity mean for Ouchterlony Immunodiffusion tests?
Antibody preparation recognizes identical
antigenic epitopes
what do lines of non-identity mean for Ouchterlony Immunodiffusion tests?
- Lines extend equally on both sides of the wells, diffuse past each other
- Antibody preparation recognizes different antigens or antigenic epitopes
what do lines of partial identity mean for Ouchterlony Immunodiffusion tests?
When antigens share some, but not all, epitopes (parts recognized by the antibody)
what is Radial Immunodiffusion?
used to measure the concentration of proteins or antibodies , by observing how it diffuses through a gel matrix uniformly concentrated with anti-antibody where the size of the ring is proportional to the concentration of the antibody
what are monoclonal antibodies?
highly specific and identical antibodies produced by a single clone of immune cells.
what is immunohistochemistry?
combines antibody specificity with histological analysis to detect and localize proteins within tissue samples by conjugating antibodies with a fluorescent tag
what is flow cytometry (fluorescence activated cell sort FACS)?
- laser equipment that detects fluorescence on individual cells one by one
- multicolor staining to detect more than one antigen simultaneously
what is enzyme linked immunosorbent assay (ELISA) ?
used in many laboratories to determine whether a particular antibody is present in a patient’s blood sample by conjugating an enzyme to a secondary antibody
what is western blotting?
technique used to detect specific proteins in a sample. It combines gel electrophoresis (to separate proteins by size) with antibody-based detection (to identify the protein of interest).
what is radioimmunoassay?
technique used to measure the concentration of antigens in a sample at very low concentrations by using radioactive isotopes
*labeled and unlabeled antigens compete for binding
what is the complement fixation assay?
detects the presence of either a specific antibody or antigen in a patient’s serum. It was widely used to diagnose infections
