Agglutination Flashcards
• It provides flexible and useful method for semi quantitating of either antigen or antibody concentration.
Agglutination test
• It is one of important laboratory method to detect antigen antibody reaction.
Agglutination test
• The reaction occurs between insoluble antigen and appropriate antibody.
Agglutination
Agglutination
• The reaction will results in forming…
• Antibodies that produce such reactions are called…
aggregate or agglutinate
agglutinins
Stages of agglutination reaction
Primary phage- Sensitization
Secondary phase- Lattice formation
• Antibody reacts with single antigenic determinants on or close to particle surface
• It is a rapid and reversible reaction.
• Based on Law of Mass Action
Primary phage- Sensitization
• A single antibody molecule binds to antigenic determinants on adjacent particles.
• The visible reaction occur under appropriate conditions and over time, particles remain connected and interconnected by antibody bridge.
Secondary phase- Lattice formation
•_____ is 700 times more efficient in agglutination than____ (Restricted hinge region of IgG than IgM)
IgM
IgG
An excess of antibody inhibits precipitation reactions, such excess can also inhibit agglutination reactions; this inhibition is called the…
prozone effect
combination of an insoluble particulate antigen with its soluble antibody
- forms antigen-antibody complex
- particles clump/agglutinate
• used for antigen detection
Active/Direct agglutination test
Examples
> The particle antigen may be a bacterium. e.g.: Serotyping of E. coli, Salmon using a specific antiserum.
The particle antigen may be a parasite. e.g.: Serodiagnosis of Toxoplasmos The particle antigen may be a red blood cell. e.g.: Determination of blood group
Direct agglutination
• Converting a precipitating test to an agglutinating test
• Chemically link soluble antigen to inert particles such as LATEX carbon, gelatin, silicates or RBCs.
Passive Agglutination Test
• Particle size- 7um to 0.8um
• Addition of specific antibody will cause the particles to agglutinate
Passive Agglutination Test
• Examples: RA factor, antinuclear antibodies (ANA) - detects autoimmnity, ASO, Spirochete antibody(TPHA).
Passive agglutination
E.g. Rose waaler test -detects rheumatoid arthritis
• RA factor in rheumatoid arthritis patients acts as antibody to human gamma globulin.
• It can agglutinate red cells coated with globulins
• Antigen is sheep RBCs suspension sensitized with rabbit anti sheep erythrocytes antibody (amboreceptor).
Hemeagglutination
: latex particles used as carrier molecules
Eg: antigen coated latex particles are used in detection of ASO, S.agalactiae, Clostridium difficile toxins A and B, rotavirus
Antibody coated latex particles are used in detection of CRP, RA factor, HCG.
Latex agglutination
• Used for syphillis
• Carbon is the carrier particle
• Cardiolipin antigen is coated with charcoal (carbon)
• Detect reagin - an antibody like substance in the plasma of syphillis
RPR or rapid plasma reagin
• Antibody is attached to the particulate carrier. One of the most commonly used laboratory tests that involves latex particle agglutination is the procedure for C-Reactive Protein (CRP).
Reverse Passive Agglutination test
: antibody linked to LATEX e.g. Lancefield grouping in Streptococci
• Reverse PAT
• When a particulate antigen is mixed with its antibody in the presence of electolytes at a suitable temperature and pH, the particles are clumped or agglutinated
Agglutination reaction
CRP
Antibody or Antigen?
Antigen
