Question

Match the images and the steps of ELISA

a. A substrate is present which the enzyme cleaves and a colored reaction is produced
b. Enzyme linked antibody binds to its specific complementary antigen.
c. Blood serum from the patient is added and incubated for 30 minutes (wash)
​d. The well is first coated with an antigen and then washed

• A. $a\Rightarrow 3.,b\Rightarrow 4.,c\Rightarrow 1.,d\Rightarrow 2$
• B. $a\Rightarrow 4.,b\Rightarrow 3.,c\Rightarrow 2.,d\Rightarrow 1$
• C. $a\Rightarrow 4.,b\Rightarrow 1.,c\Rightarrow 3.,d\Rightarrow 2$
• D. $a\Rightarrow 2.,b\Rightarrow 4.,c\Rightarrow 3.,d\Rightarrow 2$

Answer 1

The correct option is A $a\Rightarrow 3.,b\Rightarrow 4.,c\Rightarrow 1.,d\Rightarrow 2$

If a person has AIDS then he will produce antibodies against it which is usually Immunoglobulin G or IgG. So in this experiment, this antibody is detected.
First the ELISA plate is coated with an antigen and then washed to remove unbound antigen. Then the serum is extracted from the patient and added to the well. The blood of the patient will have IgG present in it if the patient is infected. This blood is then incubated for some time and then washed to remove antibody which have bound to the walls of the well and not the antigen. This removes non-specific binding. Now an enzyme linked anti IgG is added and allowed to bind to the IgG from the blood serum sample. And then the well is washed again. Now a substrate is present in the well which will react with the enzyme and produce a colored reaction. If the colored reaction does not occur then it means no antibodies were present in blood plasma and the person does not have AIDS.