Each of these variants can bind to a different antigen. This region is known as the hypervariable region. Though the general structure of all antibodies is very similar, a small region at the tip of the protein is extremely variable, allowing millions of antibodies with slightly different antigen binding sites to exist. Five different antibody isotypes are known in mammals, which perform different roles, and help direct the appropriate immune response for each different type of foreign object they encounter. There are several different types of antibody heavy chains, and several different kinds of antibodies, which are grouped into different isotypes based on which heavy chain they possess. Each antibody binds to a specific antigen an interaction similar to a lock and key.Īntibodies are typically made of basic structural units-each with two large heavy chains and two small light chains. Light chains are in lighter blue and orange, heavy chains in darker blue and orange. Figure: Antibodies bind to specific antigens: Schematic diagram of an antibody and antigens. Several complex genetic mechanisms have evolved that allow vertebrate B cells to generate a diverse pool of antibodies from a relatively small number of antibody genes. Although a huge repertoire of different antibodies is generated in a single individual, the number of genes available to make these proteins is limited by the size of the human genome. It has been estimated that humans generate about 10 billion different antibodies, each capable of binding a distinct epitope of an antigen. It is the variety in their amino acid composition that allows them to interact with many different antigens. Successful recognition and eradication of many different types of microbes requires diversity among antibodies (glycoproteins belonging to the immunoglobulin superfamily). Virtually all microbes can trigger an antibody response. V(D)J recombination: Also known as somatic recombination, this is a mechanism of genetic recombination in the early stages of immunoglobulin (Ig) and T cell receptors (TCR) production of the immune system.

A major component of the process of affinity maturation, SHM diversifies B cell receptors used to recognize foreign elements (antigens) and allows the immune system to adapt its response to new threats during the lifetime of an organism. Somatic hypermutation: a cellular mechanism by which the immune system adapts to the new foreign elements that confront it (for example, microbes).B cells expressing antibodies with a higher affinity for the antigen will outcompete those with weaker affinities (called affinity maturation).

Point mutations can result in the production of antibodies that have a lower or higher affinity with their antigen than the original antibody.

As a consequence of these processes any daughter B cells will acquire slight amino acid differences in the variable domains of their antibody chains.This serves to increase the diversity of the antibody pool and impacts the antibody’s antigen-binding affinity.The second stage of recombination occurs after the B cell is activated by an antigen.In these rapidly dividing cells, the genes encoding the variable domains of the heavy and light chains undergo a high rate of point mutation, by a process called somatic hypermutation.During cell maturation, the B cell splices out the DNA of all but one of the genes from each region and combine the three remaining genes to form one VDJ segment. The first is called V(D)J (variable, diverse, and joining regions) recombination. Antibodies obtain their diversity through 2 processes.Successful recognition and eradication of many different types of microbes requires diversity among antibodies, a result of variation in amino acid composition that allows them to interact with many different antigens. Virtually all microbes can trigger an antibody response.

Steps in antibody production