What are antibodies?

Antibodies – also known as immunoglobulins or short: Ak or Ig – are important components of the body’s own defence system, which are formed by the B cells or plasma cells, a subclass of lymphocytes. This is a group of proteins formed by the human organism which serve to defend the body against foreign material. Normally this foreign material corresponds to pathogens such as bacteria, viruses or fungi.

However, components of the red blood cells, the erythrocytes, can also be recognised and eliminated. A pathological immune response is found, for example, in an allergic reaction or in an autoimmune disease. Depending on their function and place of production in the body, they can be divided into five classes: IgA,IgG,IgM,IgE,IgD.

Ig stands for immunoglobulin. This describes a group of proteins into which the antibodies also fall. The antibodies are part of the specific immune defence.

This means that the antibodies are only responsible for a specific antigen. In contrast, the blood cells are part of the cellular immune defence, the unspecific immune response. More precisely, the antibodies are formed by B-lymphocytes, a subgroup of leukocytes.

The antibodies are able to recognize and bind antigens. The antigens are located on the surface of the material to be eliminated. Each antibody has a specific binding site for a particular antigen.

Therefore, each antibody can recognize and eliminate a certain antigen, the variety of antibodies is accordingly very large. Immunodeficiencies can lead to a reduced formation of one or more antibodies. .


Antibodies are proteins that are composed of four different amino acid chains: two identical light and two identical heavy chains. However, each antibody is different and individual and has a highly specific function in the immune system. Each antibody formed can only recognise, bind (key-lock principle) and combat very specific structures as an antigen, so that specific antibodies are formed for every foreign substance and every pathogen that attacks the body and are present in the blood or other body fluids.

The antibodies already achieve this specialisation when they are formed by the B-cells/plasma cells: the latter come into contact with an antigen (e.g. pathogens such as bacteria or viruses) as part of the immune response or are activated by other immune cells (T-cells) that have had antigen contact, so that these immediately start to produce antibodies that have exactly the binding site required to capture the antigens from the blood. Once produced, these antibodies are released freely into the blood by the B cells, where they then start to search for “their” antigen in order to bind it and make it available for destruction by other immune cells, such as macrophages. The body’s own antibodies of the immune system are divided into 5 subclasses, the immunoglobulins G, M, A, E, and D. Artificially produced or animal-derived antibodies can also be supplied to the body from outside, e.g. as part of a therapy for diseases with a disturbed or missing immune system, as a passive vaccine against various pathogens or for various types of cancer.