ELISA

Enzyme-Linked Immunosorbent Assay (ELISA) is a sensitive immunoassay that uses an enzyme linked to an antibody or antigen as a marker for the detection of a specific protein, especially an antigen or antibody. It is a biochemical test mainly used in Immunology. It was the first most basic test to determine if an individual is positive for a selected pathogen, such as HIV.



Principles

 * 1) An unknown amount of antigen is fixed to a solid surface (inner surface of a test tube)
 * 2) Preparation of the specific antibodies coupled to an enzyme
 * 3) These antibodies will conjugate with the antigens
 * 4) Substrate is added and it will bind to the enzyme
 * 5) The subsequent reaction produces a detectable signal, most commonly a color change in the substrate.

Types

 * "Indirect" ELISA
 * Sandwich ELISA
 * Competitive ELISA
 * Multiple and Portable ELISA

Applications

 * Determination of serum antibody concentrations
 * Detection of potential food allergens (milk, peanuts, walnuts, almonds, eggs)
 * Detection of antigens (pregnancy hormones, drug allergens, mad cow disease)
 * Detection of myobacterial antibodies in tuberculosis, rotavirus and enterotoxin E. coli in feces, hepatitis B markers in the serum and gonorrhea bacteria

Links

 * ELISA
 * Animation of ELISA method
 * Brief explanation of ELISA