P4 - Agglutination Reactions

• Another type of serological reaction - Agglutination Reaction 


  Precipitation (slide tests, tube tests, immunodiffusion, electro diffusion)

  Agglutination

  Complement fixation

  RIA

  EIA

  ELISA

  Western blot
• Agglutination Reaction 


  When a particulate antigen combines with its antibody in the presence of electrolytes, at an optimum temperature and pH. The particles are clumped or agglutinated.
• The difference between precipitation reaction and agglutination reaction


  In summary, while both precipitation and agglutination reactions are serological techniques used to detect antigen-antibody interactions, precipitation involves the formation of insoluble immune complexes that precipitate out of solution, whereas agglutination involves the clumping together of particulate antigens in the presence of specific antibodies.
• Types of Agglutination Reactions 


  •Slide agglutination

  •Tube agglutination

  •Passive agglutination- Latex agglutination test

  •Reverse passive agglutination test

  •Coombs test
• Slide Agglutination


  Drop of antiserum + drop of uniform suspension of antigen = clump formation

  Visible to the naked eye

  uses: blood grouping and identification of bacterial isolates
• Blood grouping 


  •The red blood cell has on its surface different types of agglutinogens.

  •To determine the blood group of a subject, the red cells are allowed to react with sera containing known agglutinins.

  •If the RBCs agglutinate, it indicates the presence of the antigens respective for the antibodies.
• Rh Blood Grouping 


  •The Rh factor was first discovered in the Rhesus monkey.

  •It is present in 85% of human beings. The most common Rh antigen is D.

  •Rh +ve persons have the Rh antigen on the red cells.

  •Rh -ve persons have NO Rh antigens on the red blood cells.•
• Widal Test


  • Agglutination test
  • Slide test/ card test
  • Screening test for enteric fever (typhoid fever)
• Tube Agglutination


  • Standard quantitative method forthe measurement of Abs.
  • Uses : WIDAL test for Typhoid fever  - Antibodies  against O and H antigens are detected.
• Results of Widal Test - Against the O (somatic antigen)

  Negative - remains colour of the solution

  Positive = uniform, thick periphery spread over the bottom of the test tube, clear supernatant fluid

  
• Result of Widal Test = Against H antigen (flagellar antigen)


  Against the H antigen

  
• Passive Agglutination 


  •Using carrier particles, precipitation tests can be converted into agglutination tests.

  •Commonly used carrier particles :

  • RBC
  • Latex
  • Bentonite
• Latex Particle Agglutination Test 


  •Polystyrene latex particles coated with antigen 

  •Visible clumping

  Application: Employed in the clinical laboratory for detection of 

  • ASO (Anti-streptolysin O ) – for diagnosis of ARF (acute rheumatic fever)
  • CRP (C-Reactive protein)
  • The common causative agents of bacterial meningitis: Streptococcus pneumoniae, Haemophilus influenzae and Neisseria meningitides  (types A and C)
• Result of Latex Agglutination Test

  Positive and negative

  
• Hemagglutination


  •RBCs are used as antigens  e.g Paul Bunnell test   

  OR

  •RBCs act as carrier particle and coated with antigen.

  •Eg: TPHA (Treponema Pallidum hemagglutination assay)- for diagnosis of syphilis
• TPHA full form 


  Trepanoma Pallidum Hemagglutination Assay

  • test for syphilis - because treponema pallidum causes syphilis
• TPHA test result 


  RESULTS