Q.Give the full form of ELISA. Which disease can be detected using it? Discuss the principle underlying the test.

ELISA stands for Enzyme-Linked Immunosorbent Assay. This diagnostic technique is commonly used to detect various diseases, including AIDS, which is caused by the Human Immunodeficiency Virus (HIV).

The principle underlying ELISA is based on the antigen-antibody interaction.

• When an individual is infected by a pathogen, their immune system produces specific antibodies in response.
• ELISA works by detecting the presence of these antibodies, or sometimes the antigens themselves, in the patient's blood serum. …

In the realm of disease diagnosis, particularly for infectious conditions, early and accurate detection is paramount. It allows for timely intervention, better management of the disease, and prevention of its spread. Among the various diagnostic tools available, one highly sensitive and widely employed technique is ELISA.

ELISA stands for Enzyme-Linked Immunosorbent Assay.

The fundamental principle underlying the ELISA test is the highly specific interaction between an antigen and its corresponding antibody. Our immune system produces antibodies in response to foreign substances, known as antigens, such as those found on pathogens like viruses or bacteria. ELISA leverages this natural biological recognition system to identify the presence of either these specific antigens (components of the pathogen itself) or the antibodies produced by the patient's body against that pathogen.

Here's how the principle works:

• Antigen-Antibody Specificity: The test relies on the fact that a particular antibody will bind only to its specific antigen, much like a key fits only one lock.
• Immobilization: In an ELISA test, either known antigens or known antibodies are first attached (immobilized) to a solid surface, typically the wells of a microtiter plate.
• Sample Addition: A patient's sample, such as blood serum, is then added to these wells.
  • If the test is designed to detect antibodies in the patient's serum, and the patient has been exposed to the pathogen, their antibodies will bind to the immobilized antigens in the well.
  • If the test is designed to detect antigens of the pathogen, and the pathogen is present, its antigens will bind to the immobilized antibodies in the well.
• Enzyme Linkage and Detection: After washing away unbound components, a secondary antibody is added. This secondary antibody is conjugated (linked) to an enzyme.
  • If the target (either the patient's antibody or the pathogen's antigen) is present and has bound to the well, this enzyme-linked secondary antibody will then bind to it.
  • Finally, a specific substrate for the enzyme is added. The enzyme acts on this substrate, causing a chemical reaction that produces a detectable signal, most commonly a change in colour. …

Method — expand, then link cause→signal→detection

Expand: Enzyme-Linked Immuno-Sorbent Assay.

Chain: pathogen (e.g. HIV) enters body → immune system makes antibodies against its antigens (the cause) → ELISA's enzyme-linked antibody produces a colour change when it binds either the antigen or the patient's anti …