ELISA is based on the principle of:

The correct answer is Option (4) → Antigen-antibody interaction

ELISA stands for enzyme linked immuno-sorbent assay. It is a test used to find out whether a person has an infection. It works by looking for the pathogen’s antigens, or for the antibodies the body has made against the pathogen.

(1) Protein-lipid interaction — Incorrect. Lipids play no part in the test.

(2) Antigen-antigen interaction — Incorrect. An antigen is a foreign molecule that the immune system reacts to. Two antigens do not bind each other.

(3) Antibody-lipid interaction — Incorrect. An antibody is a protein that recognises one particular antigen. It does not recognise lipids.

(4) Antigen-antibody interaction — Correct. An antibody binds only to its own antigen. When this binding is detected, the infection is confirmed.

Note: A similar question was also asked in CUET (UG) 2026 on 14-05-2026 (Slot 2), in CUET (UG) 2025 on 20-05-2025 (Slot 1) and on 13-05-2025 (Slot 1), and in CUET (UG) 2024 on 29-05-2024 (Slot 1).

NCERT Extract:
Molecular Diagnosis – …