Which one of the following diagnostic techniques is based on the principle of antigen-antibody interaction?

Enzyme-linked immuno-sorbent assay

The correct answer is Option (3)- Enzyme-linked immuno-sorbent assay

ELISA stands for "Enzyme-Linked Immunosorbent Assay." It is a widely used laboratory technique employed for the detection and quantification of specific proteins, antibodies, antigens, or other substances. The assay is based on the principle of the interaction between antibodies and antigens. Infection by pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesized against the pathogen.

ELISA is a versatile and sensitive technique widely used in immunology, clinical diagnostics, and research for applications such as detecting antibodies in blood, identifying pathogens, and quantifying specific proteins.