Antigens

Background

Antigens are large molecules such as chemicals, toxins, and drugs that are found on the surface of cells, bacteria, fungi, viruses, and non-living substances. The immune system detects antigens and releases antibodies that recognize and initiate the destruction of foreign substances that contain antigens.  Antigens can be produced by a variety of bacteria, viruses, and cells.

Antibody production is triggered by the detection of antigens. For example, the recognition of pollen or molecules from food can result in an allergic response by the body. Upon entering a cell, an antigen is coupled to a histocompatibility complex and presented on the surface of the cell to be recognized by antibodies. Each antibody matches an antigen like a key to a lock. The fit of the antibody can be precise, while other times it can be more general. The role of antibodies is to target an antigen and mark it for termination.

Antibodies reside various bodily fluids and are gamma globulin proteins. The body uses antibodies to identify and neutralize foreign objects in the body, such as viruses or bacteria. This mechanism is like a built-in antibiotic for the immune system.  Antibodies are classified as a family of large molecules known as immunoglobulins.  Globulins consist of polypeptide chains or amino acids.   Each antibody is constructed of 2 light chains and 2 heavy polypeptide chains that form the arms of a “Y” shape.  These arms are antigen specific and vary from one antibody to another.

Other types of antibodies include:

Autoantibodies – rather than fighting foreign antigens, autoantibodies attack the body’s own cells

Antinuclear antibodies – a group of autoantibodies that attack structures inside the nucleus of the cell.

Therapeutic Antibodies

Antibodies can be used in humans for therapeutic purposes – introducing specific antibodies can help fight viral infections, cancers, and a variety of other problematic conditions. Despite their promising nature, antibody therapies have been progressing rather slowly, even with recent advances in approved medicines. One of the most promising applications has been the development of monoclonal antibodies, which present a highly specific use of antibodies that can be used to target specific cancer cells. Limitations of antibody therapy include antibody size, problems with efficiency, and in vivo penetration for the treatment of specific cancers.

Monoclonal antibodies are created by combining single antibody-forming cells with tumor cells that are grown in culture.  The new cell is called a hybridoma cell and each one of the new cells produces a large quantity of identical antibody molecules. Growing these cells in culture makes it possible to produce large quantities of identical antibody molecules. This can be used to target highly specific foreign particles should they enter an organism. There are several potential issues though, for example, the antibodies may be targeted by an organism’s immune system. This specific problem can be resolved by changing the origin of the hybridoma to be that of a recipient organism.

Currently there are several antibody therapeutics in the market. Some are now undergoing clinical testing, while others have been approved as standard of care therapies. These include monoclonal antibodies such as ipilimumab, pembrolizumab, and nivolumab.

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