MP Board · Class 12 · Biology · Biotechnology and its ApplicationsWhat is ELISA? Mention the principle and medical application of ELISA test in diagnosing diseases.

ELISA stands for Enzyme-Linked Immunosorbent Assay. It is an analytical biochemistry assay that uses antibodies and color change to identify a substance, usually an antigen. ELISA is widely used as a diagnostic tool in medicine to detect pathogens, hormones, proteins, and antibodies in patient samples. \nThe principle of ELISA is based on the antigen-antibody interaction. Infection by a pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) produced by the pathogen, or by detecting the antibodies synthesized against the pathogen in the patient's serum. If the specific antigen is present in the sample, it binds to the corresponding antibody attached to a solid surface. An enzyme is conjugated to a secondary antibody that binds to the target complex. Upon adding a specific chromogenic substrate, the enzyme catalyzes a chemical reaction resulting in a measurable color change, confirming a positive diagnosis. \nA primary medical application of ELISA is the detection and screening of HIV (Human Immunodeficiency Virus) infection in blood samples. It is also used to diagnose various infectious diseases, hormone disorders, and autoimmune conditions where specific antibodies or antigens need to be quantified with high sensitivity and specificity.