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Advancing diagnostics for lupus nephritis

The nature of a typical clinical test for lupus nephritis (LN), an inflammation of the kidneys and a leading cause of mortality in lupus patients, is fraught with difficulty. The invasive renal biopsy can be painful and may ...

Diseases, Conditions, Syndromes

New study shows common antibody therapy has anti-SARS-CoV-2 antibodies

Researchers at the University of Texas Medical Branch recently confirmed the presence of neutralizing antibodies to SARS-CoV-2 in a common subcutaneous antibody therapy (Hizentra) used to treat immunocompromised or immunodeficient ...

Immunology

Understanding allergies

Do you blow your nose and rub your itchy eyes more than usual in the spring? Chances are you have hay fever, also called allergic rhinitis, an allergic response that has absolutely nothing to do with hay and everything to ...

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New Kawasaki disease guideline for physicians released

The American College of Rheumatology (ACR), in partnership with the Vasculitis Foundation (VF), released a new guideline for the management of Kawasaki disease that addresses diagnostic issues relating to Kawasaki disease, ...

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Living guidelines for care of kids and teens with COVID-19

Living guidelines for the clinical care of children and adolescents with COVID-19 have been developed with 20 recommendations including the use of corticosteroids as first-line treatment for those who require oxygen. A summary ...

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Antibody

An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen. Each tip of the "Y" of an antibody contains a paratope (a structure analogous to a lock) that is specific for one particular epitope (similarly analogous to a key) on an antigen, allowing these two structures to bind together with precision. Using this binding mechanism, an antibody can tag a microbe or an infected cell for attack by other parts of the immune system, or can neutralize its target directly (for example, by blocking a part of a microbe that is essential for its invasion and survival). The production of antibodies is the main function of the humoral immune system.

Antibodies are produced by a type of white blood cell called a plasma cell. Antibodies can occur in two physical forms, a soluble form that is secreted from the cell, and a membrane-bound form that is attached to the surface of a B cell and is referred to as the B cell receptor (BCR). The BCR is only found on the surface of B cells and facilitates the activation of these cells and their subsequent differentiation into either antibody factories called plasma cells, or memory B cells that will survive in the body and remember that same antigen so the B cells can respond faster upon future exposure. In most cases, interaction of the B cell with a T helper cell is necessary to produce full activation of the B cell and, therefore, antibody generation following antigen binding. Soluble antibodies are released into the blood and tissue fluids, as well as many secretions to continue to survey for invading microorganisms.

Antibodies are glycoproteins belonging to the immunoglobulin superfamily; the terms antibody and immunoglobulin are often used interchangeably. Antibodies are typically made of basic structural units—each with two large heavy chains and two small light chains. 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. 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.

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 tip structures, or antigen binding sites, to exist. This region is known as the hypervariable region. Each of these variants can bind to a different target, known as an antigen. This enormous diversity of antibodies allows the immune system to recognize an equally wide variety of antigens. The large and diverse population of antibodies is generated by random combinations of a set of gene segments that encode different antigen binding sites (or paratopes), followed by random mutations in this area of the antibody gene, which create further diversity. Antibody genes also re-organize in a process called class switching that changes the base of the heavy chain to another, creating a different isotype of the antibody that retains the antigen specific variable region. This allows a single antibody to be used by several different parts of the immune system.

This text uses material from Wikipedia, licensed under CC BY-SA