Question

Which of the following types of $ELISA$ contain the following steps?
Antigen binding, Blocking, Primary antibody, Secondary antibody, Enzyme-linked antibody, Substrate, Colorimetric reading (Represented in diagram).

• A. Direct $ELISA$
• B. Indirect $ELISA$
• C. Competitive $ELISA$
• D. Sandwich $ELISA$

Answer 1

Answer: (D)

Sandwich $ELISA$ is a less common variant of $ELISA$, but is highly efficient in sample antigen detection. The sandwich $ELISA$ quantify antigens between two layers of antibodies. The antigen to be measured must contain atleast two epitopes capable of binding to two antibodies. The basic steps involved are as follows :
(i) Plate is coated with captured antibody.
(ii) Sample is added, and any antigen present in the sample binds to captured antibody.
(iii) Detecting antibody is added, and binds to antigen.
(iv) Enzyme-linked secondary antibody is added that binds to detecting antibody.
(v) Substrate is added which gets converted by enzyme to detectable colour product that can be measured through colorimeter.