Immunoglobulin superfamily

In Encyclopedia by Jacqueline Bureau Views: 15

Immunoglobulin superfamily is a large group of membrane but also soluble glycoproteins majority, involved in the phenomena of recognition, binding and cell adhesion. These generally membrane proteins have in common several characteristics “immunoglobulin” areas in their tertiary structure. Note that disulfide just close the characteristic loop of immunoglobulins. This family contains proteins such as molecules binding to antigens (antibodies and the major histocompatibility complex molecules), molecules of Costimulation, a co-receptor, binding molecules, certain cytokine receptors. These molecules have a crucial role in the interactions between cells involved in the immune system. Indeed, the major complex of histocompatibility of type I and type II and antibodies are members of this superfamily. Some immunoglobulins are the gateway of virus such as (recipient of the CD4 molecule) AIDS virus or to rabies [REF. necessary].

Attention: most of the members of the immunoglobulin superfamily are not immune effectors because they have no variable part and not of Antigen binding.

Immunoglobulins are of small proteins called gamma globulin, present in body fluids. They are molecules of adhesion with activity “antibodies”.
Blood determination of specific immunoglobulin can establish or confirm certain medical diagnoses.

Biomolecular nature

Immunoglobulins (Ig – CAM) superfamily is a large group of small proteins (glycoproteins), often membrane but also found in solution in the liquids or mucus in the body.
This family is it even to the Group of gamma globulins are found in the blood serum and in other liquids (including cerebrospinal fluid) or mucus in the body.
These generally membrane proteins have in common several (from 1 to 7) structural domains extracellular so-called “immunoglobulin” features in their tertiary structure (a disulfide bridge closes the characteristic loop of immunoglobulins).

There are

• IgA
• RMI
• IgE
• IgG
• IgM

Functions

They are involved in

• the phenomena of recognition,
• links and events of cell adhesion; These proteins are called Ig – CAM (for “Cell adhesion molecule”).

This family contains proteins such as

• molecules binding to antigens (antibodies)
• the major histocompatibility complex molecules,
• molecules of Costimulation,
• a co-receptor,
• binding molecules,
• some cytokine receptors.

Immune role

They play a crucial role in the interactions between cells involved in the immune system; the major complex of histocompatibility of type I and type II and antibodies are members of this superfamily. Severe allergic grows immunoglobulin levels, but can also translate a parasitosis (of the digestive tract in General).

• Immunoglobulin G (IgG) are 75-80% of our circulating antibodies. They are produced in response to an antigen (body not recognized by the body). They protect the body against bacteria, viruses, and some toxins in the blood or lymph.
  They set the add-in (components of the immune system) and play a role in the response brief, basis of sustainable immunity, allowing the vaccination. They cross the placental barrier and allow “passive immunity” by the immune system of the mother to the fetus.
• Immunoglobulin A (IgA) form a barrier preventing most of the pathogens to bind to the cells of the mucous membranes and skin. (They are present in glandular secretions and type mucus and in particular in the saliva, tears, breast milk (colostrum), nasal secretions, gastrointestinal secretions and respiratory tract). IgA deficiency (which can have a genetic origin) can lead to infections of the respiratory tract-level higher (rarely in the lower level), but elevated serum IgG and IgM can naturally part compensate this deficit.
• Immunoglobulin M (IgM) are immunoglobulins produced by certain white blood cells (plasma cells) in response to antigens. Abnormally high blood levels of IGM is the sign of a current infection.
• Immunoglobulin D (IgD) are almost always attached to the surface of B cells where they fix antigens.
• Immunoglobulin E (IgE) are larger than the immunoglobulins g produced by certain white blood cells (plasma cells), in the skin, digestive, tonsils (or tonsilles) system and the respiratory tract. They are connected to two types of white blood cells (mast cell and basophil granulocytes) by a kind of stem. Antigen capture, by this immune globulin, leads to the secretion of products (including histamine) launching an inflammatory and possibly allergic reaction.

Some immunoglobulins are also the door of entry of such viruses:

• (recipient of the CD4 molecule) AIDS virus
• virus rabies [REF. necessary].