Question

What are the three main functions of antibodies?

Answer 1

An antibody (Ab), also known as an immunoglobulin (Ig), is a big, Y-shaped protein that helps the immune system recognize and eliminate foreign substances like bacteria and viruses. The antigen, which is a unique molecule of the pathogen, is recognized by the antibody. Each point of an antibody’s “Y” carries a paratope (similar to a lock) that is specific for one epitope (similar to key).

Complete answer:
Antibodies are glycoproteins that belong to the immunoglobulin superfamily and are normally made up of two big heavy chains and two small light chains. Most antibodies are monomers, with a single “Y” shaped component, although other antibodies can be dimers (two subunits) or pentamers (five subunits).
Antibodies contribute to immunity in three ways:
By binding to pathogens and preventing them from entering or damaging cells (neutralisation);
By coating pathogens and stimulating their removal by macrophages and other cells (opsonization);
And by triggering pathogen destruction by stimulating other immune responses such as the complement pathway. The complement system initiates a series of protein synthesis events that either opsonize a pathogen for phagocytosis or directly lyse it by producing a membrane attack complex.
On a macrophage, neutrophil, or natural killer cell, the antibody expresses the tail for an Fc receptor during opsonization.
Antibodies function as scouts for the immune system. They locate antigens, stick to them, and identify the exact type of antigen for the immune system to eliminate. Each antibody is designed to bind to a single antigen and is equipped with receptors that can only bind to that antigen.

Note:
To avoid autoimmunity, an antibody can signal immune cells to send antibody fragments to T cells or downregulate other immune cells. Activated B cells can develop into either antibody-producing plasma cells that secrete soluble antibodies or memory cells that stay in the body for years, allowing the immune system to remember an antigen and respond more quickly in the future.