Elisa-Principle,Types ,Immunology

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 ELISA 

  • Its simple ,nearly as sensitive as radioimmunoassay
  • It has wide range of application
  • Used for detection of specific antigen/antibody

PRINCIPLE:

  • Enzyme is used to detect antigen antibody reaction 
  • Colour change is the indication for detection
  • Its carried in polyvinyl plates ,polystyrene plate.

TYPES

1) SANDWICH ELISA:

  1. In a microtitre plate ,wells are coated with specific antibody eg- e.coli -antigen test,specific antibody is placed.




  1. Specimen to be tested is added
  2. If the specimen contains suspected antigen (antigen-antibody reaction)
  3. to detect this reaction ,anti-serum conjugated with an enzyme is added it binds to antigen that's already attached to antibody
Positive results :
  • Enzyme+antiserum  act on substrate produce colour that's read by elisa reader.
2) INDIRECT ELISA:
  • Microtitre plate wall coated with specific antigen that help in detection of antibody
  • If positive antigen -antibody reaction occur 



  • Substrate: antibody to antigen conjugated , enzyme is added
  • Substrate is added to detect colour change positive 
3) COMPETITIVE ELISA:
  • No colour change -positive
  • colour change - negative
  • HIV antibodies are checked through competitive elisa
  1. Titre coated with HIV antigen
  2. Serum to be tested is added
  3. If it contains its specific antigen,antigen to antibody reaction takes place
  4. In previous positive reaction there is no antigen that's left over for these to react with it therefore removed while washing away
  5. When substrate are added ,no enzyme labelled antibodies are left over to react as they are washed away
  6. Therefore no colour change
  7. Serum positive - no free  antigen for these enzyme labelled antibodies to react 
USE OF ELISA:
  1. Detection of HIV antibodies,HBV marker in serum
  2. Detection of Rotavirus and enterotoxin of E.coli in faeces
  3. Detection of mycobacterial antibodies in tuberculosis.



AIM OF THIS POST:
Today we started with what a elisa is ,principle,types of elisa in detail with  easy diagrams . Yes,this is a very short post but i hope the core concepts were explained clearly .If you like this post do let me know in the comment section below .
Here at stencildent we are celebrating this week as #classification week 
Today being day 4 we have discussed about different types of elisa.

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