Humoral immune response
| Parent |
| Immune response |
| Subordinate |
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Complement-dependent cytolysis Coagulation Antimicrobial humoral immune response IG-mediated immune response |
| Gene Ontology |
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| QuickGO |
The humoral immune response (from Latin [h] umor = moisture also juice, liquid ) is the part of the body's immune response that is mediated by the non-cellular components of body fluids. Together with the cellular immune response , it forms the immune system of higher living beings.
Multicellular organisms have a number of different ways of fighting off substances that are foreign to the body. There are many immune cells that help ensure that living beings do not get sick. The humoral immune response takes place in the body's liquid media, e.g. B. in the blood or in the lymph and is used to fight viruses and bacteria in the extracellular space.
Lymphocytes are a group of these defense cells found in mammals . There are two large families of lymphocytes, the B lymphocytes and the T lymphocytes . While the T-lymphocytes are able to destroy or eliminate whole cells or parasites , the B-lymphocytes use a different defense method. They produce proteins - so-called antibodies , which bind to the antigens and render them harmless. When a B-lymphocyte recognizes an antigen, the structural features of the pathogen are presented on its surface. As soon as this happens, the B-lymphocytes multiply and differentiate into plasma cells and B-memory cells. The plasma cells begin to produce specific antibodies and release them into the body fluids. These antibodies then combine with the surface proteins of the antigen and thus mark the exogenous substance. This ultimately leads to its destruction or excretion.
The humoral immune response can basically be divided into three phases:
The humoral immune response kicks in when the body is infected by antigens. Macrophages are permanently in the tissues and vascular systems in search of foreign bodies.
Activation phase
When an antigen ( virus or bacteria ) enters the body, macrophages recognize it as foreign by scanning the surface. The macrophages then enclose and absorb the antigen (phagocytosed) and then enzymatically decompose (lysed) in the cell plasma .
The macrophages then present fragments ( epitopes ) of the antigen on the surface at the MHC class II receptors of their cell membrane. Here a distinction is made between endogenous and exogenous substances by MHC class II proteins (self-foreign differentiation). By releasing cytokine IL 1 ( interleukin-1 ), a type of hormone of the macrophages, the T helper cells (CD4 + cells) are brought into contact with the antigen presented on the MHC class with their T cell receptors. II receptor to include. The contact is intensified by CD4 . By releasing interleukin-2 , the activated T helper cells are made to differentiate. As a result, some T helper cells also transform into regulatory T cells, which after some time terminate the immune response by releasing special proteins.
Differentiation phase
An activated T helper cell makes contact with a B lymphocyte, which has recognized the same antigen (B epitope) with the help of its immunoglobulin receptor and now in turn presents the T epitope via MHC class 2 on its surface, and activates it the release of cytokines. The activated B-lymphocyte forms B-plasma cells and B-memory cells. The B memory cells are long-lived and ensure a faster and more effective immune response in secondary contact with the antigen. The B plasma cells produce antibodies that render the pathogen harmless. The production of these antibodies takes place in the rough endoplasmic reticulum (ER). There a kind of “basic shape” is translated on the ribosomes, which can only bind to the epitopes of the antigens through the use of specific enzymes that cut the variable epitopes according to the template (the epitopes of the antigens).
From the primary contact with an antigen to the occurrence of relevant amounts of antibodies, it typically takes several days in humans, but depending on the antigen and many other factors, weeks (latency period).
Effector phase
Antigen-antibody reaction : Antibodies bind a specific epitope on the antigens through their variable but specific paratopes. Since an antibody has two identical binding sites, it can bind up to two identical antigen molecules. Conversely, if the antigenic material has several antigenic sites on the same body, a large network (immune complex, see also agglutination ) of antigens and antibodies can result. If antigen-occupied cells are involved, this complex can become so large that it is no longer soluble and precipitates (see also hemagglutination , e.g. in the blood ). The formation of immune complexes activates the complement system . In the other sequence are macrophages which attracted bind to the constant epitopes of the antibodies parts adopt the immune complex by phagocytosis and build these from.
literature
- Charles Janeway , Paul Travers, Mark Walport, Mark Shlomchik: Immunology. 5th edition, Spektrum Akademischer Verlag, Heidelberg 2002, ISBN 3-8274-1079-7 ; Online version in English , 5th edition, 2001.
