Antibody structure render

Antibodies, or immunoglobulins, are Y-shaped proteins crucial for the immune system to neutralize pathogens.

About this subject

Antibodies, also known as immunoglobulins (Ig), are glycoproteins produced by B lymphocytes in response to antigens. Structurally, each antibody has two heavy chains and two light chains, forming an antigen-binding fragment (Fab) and a crystallizable fragment (Fc). The Fab region recognizes specific antigens, while the Fc region interacts with immune cell receptors and the complement system. Mammals have five main antibody classes: IgG, IgA, IgM, IgE, and IgD, each with distinct roles in immune defense.

IgG is the most abundant antibody in blood and extracellular fluids, playing a key role in humoral immunity and immunological memory. IgA is found in mucosal secretions like saliva and breast milk, protecting epithelial surfaces. IgM is the first antibody produced during a primary infection and serves as an antigen receptor on B cells. IgE defends against parasites and is involved in allergic reactions. IgD mainly functions as a receptor on the surface of immature B cells.

The discovery of antibody structure earned Rodney Porter and Gerald Edelman the Nobel Prize in 1972. Since then, molecular biology advances have enabled the production of monoclonal antibodies, widely used in diagnostics and therapy, such as in cancer and autoimmune disease treatment. Antibody diversity is generated by genetic rearrangements and somatic mutations, allowing recognition of millions of different antigens.

Frequently Asked Questions

What are the main classes of antibodies and their functions?

The five main classes are IgG, IgA, IgM, IgE, and IgD. IgG is the most abundant and provides lasting immunity. IgA protects mucous membranes, IgM acts in primary response, IgE mediates allergic reactions and parasite defense, and IgD functions as a receptor on immature B cells.

How do antibodies recognize specific antigens?

Antibodies have a variable region in the Fab portion that binds to a specific epitope of the antigen with high affinity and specificity, due to gene rearrangement and somatic hypermutation in B lymphocytes.

What are monoclonal antibodies and what are they used for?

Monoclonal antibodies are produced by clones of B lymphocytes, identical to each other, and used in diagnostics and therapies, such as cancer treatment (e.g., rituximab) and inflammatory diseases (e.g., adalimumab).