Transcript Serelogy

Classification of antigen-antibody interactions:
- Primary serological tests: (Marker techniques) e.g.
Enzyme linked immuonosorbent assay (ELISA)
Immuno flurescent antibody technique (IFAT)
Radio immuno assay (RIA)
- Secondary serological tests: e.g.
Agglutination tests
Complement fixation tests (CFT)
Precipitation tests
Serum neutralization tests (SNT)
Toxin-antitoxin test
Agglutination :
- Antigens are whole cells (eg. RBC or bacteria).
- Antibodies cross-link the antigens.
- Types of tests :
- Rapid plasma test (syphilis).
- Cold agglutinin test (mycoplasma).
- Weil-Felix test (rickettsial).
- Latex agglutination test (pregnancy).
Agglutination : ( continued )
- Agglutination reactions involve whole cell antigens, while precipitation
reactions involve soluble antigens.
- Cellular/molecular
view of
agglutination and
Precipitation
reactions that
produce visible AgAb complexes.
Agglutination : ( continued )
Rapid plasma reagin ( RPR test )
- The rapid plasma reagin (RPR) test is available as a kit.
The patient's serum is mixed with cardiolipin on a plastic-coated card
that can be examined with the naked eye.
Precipitation
- Soluble antigens.
- Binding of antibody to antigen, makes the complex insoluble or visible.
- Types of test :
- Tube precipitation.
- Ouchterlony (double diffusion).
- Immunoelectrophoresis.
Precipitation : ( Continued )
- Precipitation reactions
Precipitation : ( Continued )
Ouchterlony (double diffusion)
Precipitation : ( Continued )
Precipitation curve :
Complement fixation
- Antibody (lysin), antigen, complement, and
sensitized sheep rbc are required.
- Complement is fixed to a Ab-Ag-complex.
-Fixed complement cannot participate in rbc lysis
positive reaction or identification.
Complement fixation test
Nephelometry ( Turbidimetry )
- Nephelometry is a technique used in immunology to
determine levels of IgM, IgG, and IgA.
Immunofluorescence
- A monoclonal antibody labeled with a fluorescent dye :
- Direct testing.
- Indirect testing.
Immunofluorescence testing
- An example of direct
and indirect
immunofluorescence
testing.
Common assays
- Radioimmunoassay (RIA).
- Enzyme-Linked Immunosorbent Assay (ELISA).
Radioimmunoassay (RIA)
- Antibody or antigen is labeled.
- Detect corresponding antibody or antigen.
- Competition between unlabeled and labeled
molecule.
Radioimmunoassay (RIA) : ( Continued )
Enzyme-Linked Immunosorbent Assay (ELISA)
- Safer & less costly than RIAs.
- ELISA methods can detect any infectious disease provided
if we have antibodies and antigen to any infection,
enzyme or any substance.
Enzyme-Linked Immunosorbent Assay (ELISA)
- Horseradish peroxidase or alkaline phosphatase.
- Enzyme releases dye (chromogen).
- Types of test :
- Indirect ( Non-competitive ).
- Capture or Sandwich.
- Competitive ELISA.
An example of the indirect ELISA method
Ex: detecting the presence of serum Abs against HIV
An example of the capture ELISA method
An example on competitive ELISA method