3Uses:In estimation ofhormonesDrugsEnzymesDetect Infectious microbial Ags or Abse.g. HIV, Hepatitis A, B etcTo detect the markers of tumer
4Enzyme-Linked ImmunoSorbent Assay (ELISA) Enzyme-Linked ImmunoSorbent Assay, or ELISA, is a abiochemical technique used mainly in immunology to detect the presence of an antibody or an antigen in a sample..
5Principle:in ELISA an unknown amount of antigen is affixed to a surface (solid phase), and then a specific antibody is added on the surface so that it can bind the antigen.This antibody is linked to an enzyme, and in the final step a substance is added that the enzyme can convert to and give detectable color.
6Types of ELIZA: 1-Indirect ELISA , "indirect," ELISA for detect antibodies in patient serum the steps as follow:The antigen is fixed to the surface of microtiter to make it immobile. Simple adsorption of the protein to the plastic surface is usually sufficient.The plate wells or other surface are then coated with serum samples
73-The plate is washed to remove any unbound detection antibody.. 4-Secondary antibodies conjugated to the enzyme are added to the wells.5- Wash the plate,6- Apply a substrate which is converted by the enzyme to specific color7-put stop solution8-Read the result(color) using a spectrophotometer,
8Used for testing the amount of antibody to an antigen in serum
10Direct ELIZA(Sandwich ELISA ) To detect unknown Ags in patient serumPlate is coated with a capture antibodysample is added, and any antigen present binds to capture antibodydetecting enzyme-linked antibody is added, and binds to antigensubstrate is added, so it is converted by enzyme to detectable color. then stop solution also added to stop reaction
12Add the solution containing antigen to be measured
13Competitive ELISA For the detection of HIV antibodies, the wells of microtiter plate are coated with the HIV antigen.Two specific antibodies are used, one conjugated with enzyme and the other present in serum (if serum is positive for the antibody).
14Competition occurs between the two antibodies for the same antigen. Sera to be tested are added to these wells and incubated at 37 degrees and then washed.If antibodies are present, antigen-antibody reaction occurs.Substrate is added but there is no enzyme to act on it, therefore, positive result shows no color change.
152- radioimmunoassay RIA Detected by X ray3- immunofluoresecent IFDetected by fluorescent microscopy