Discuss briefly process of Indirect ELISA.

The method of ELISA is used for the detection of the disease using the antigen and antibody interaction. The specific antigen is coated to the wells of the ELISA plate. The excess of antigens are washed with buffer. The sample which contains the antibody are added to the well. If there is specific (primary) antibody, they will bind to the antigen which is coated. The well is washed with buffer to remove the unbounded antibodies. The secondary antibody is attached which is attached with an enzyme. The secondary antibody binds to the primary antibody. The chromogenic substrate is added which is acted upon by the enzyme and the colour is produced which can be read and detected by the ELISA reader. The change and intensity of the colour can be used to detect the disease.