Protein (Part-IV)

DETECTION OF PROTEIN IN BIOLOGICAL FLUIDS:
(A) Detection of antibody:

Background Information: ELISA is a immunological technique used to measure the level of antibodies or antigen in the body fluid. It has been used in diagnostics to identify the antigen or cross reactive antibody. ELISA can be performed in two different ways to either measure antibody or antigen. These different variants are given in Figure 35.1.

1. In-direct ELISA- This setup is used to measure the level of antibodies in the serum and used to calculate the titre of the antibodies. In the in-direct ELISA setup, a known amount of antigen is coated to the well and it is incubated with the different dilutions of antibodies. The antigen bound antibody is then recognized by the secondary antibody linked to the enzyme. A colorimetric substrate is used to measure the level of antibody.

2. Sandwich ELISA- This setup is used to measure the level of antigen (such as insulin) in the serum. In the direct ELISA setup, a known amount of antibody specific antibody (capture antibody) to capture the antigen. The antigen is then recognized by the secondary antibody linked to the enzyme. A colorimetric substrate is used to measure the level of antigen.

Figure 35.1: Different types of ELISA.