Humoral immunity

As a humoral immune response ( umor of lat [h ] = moisture and juice, liquid ), the part of the immune response of the body referred to, which is mediated by the non- cellular components of body fluids. Together with the cellular immune response to form the immune system of higher animals.

Multicellular living organisms have a number of different ways to fight off foreign substances. So there are a variety of immune cells that contribute to that living things do not get sick. The humoral immune response takes place in liquid media of the body instead, eg in the blood or lymph and is used to fight viruses and bacteria in the extracellular space.

One group of these defense cells that are found in mammals, are the lymphocytes. There are two major families, lymphocytes, B lymphocytes and T lymphocytes. While the T- lymphocytes are able to destroy whole cells or parasites or eliminate the B- lymphocytes of another method of defense use. They produce proteins - or antibodies that bind to the antigens and make them harmless. When a B-lymphocyte that recognizes an antigen, the structural features of the pathogen are presented on its surface. Once this happens proliferate and differentiate into B lymphocytes into plasma cells and memory B cells. The plasma cells begin with the production of specific antibodies and hand these in the body fluids. These antibodies then combine with the surface proteins of the antigen and mark as the exogenous substance. This ultimately leads to the destruction or elimination.

The humoral immune response can be fundamentally divided into three phases:

The humoral immune response begins when an infection of the body has taken place 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, it is detected by scanning the surface of macrophages as foreign. Then, the antigen is enclosed by the first and macrophages added ( phagocytized ), and then in the cytoplasm enzymatically decomposed ( lysed ).

Then presenting macrophages fragments ( epitopes) of the antigen on the surface of the MHC class II receptors of their cell membrane. Here you will find a distinction between endogenous and exogenous substances by MHC class II proteins instead (Self - foreign distinction ). By pouring of the cytokine IL1 ( interleukin 1 ), a kind of hormone which macrophages are brought the T-helper cells (CD4 cells), to engage with their T - cell receptor contact with the presented antigen on MHC class II receptor incorporated. Contact is increased by CD4. Through the outpouring of interleukin -2, the now activated helper T cells are induced to differentiate. This also some helper T cells to transform into T- suppressor cells, which ended by distribution of specific proteins, the immune response after some time.

Differentiation phase

An activated helper T cell makes contact with a B- lymphocytes, which by means of its immunoglobulin receptor the same antigen ( B epitope ) is detected and then, in turn, presented to the T- epitope on MHC class -2 on its surface, and activates it by the secretion of cytokines. The activated forms of B lymphocyte B- cells, plasma and memory B cells. The memory B cells are durable and provide for a secondary contact with the antigen for a faster and more effective immune response. The B- plasma cells produce antibodies that make the pathogen harmless. The production of these antibodies takes place in the rough endoplasmic reticulum. There, a kind of " basic form " is translated on ribosomes, which itself can bind to the epitopes of the antigens only through the use of specific enzymes that can cope cut the variable epitopes on presentation ( the epitopes of the antigens).

Effector

Antigen -antibody reaction: antibodies bind with their variable but specific paratopes respectively a particular epitope on the antigen. Since an antibody has two identical binding sites, respectively, it can bind up to 2 identical antigen molecules. Has reversed the antigenic material several antigen- looking parts of the same body, a large network ( immune complex, see also agglutination) of antigens and antibodies result. This complex can be so large in participation of antigen- occupied cells, that it is no longer soluble and precipitates (see also hemagglutination, eg in the blood). The formation of immune complexes activate the complement system. In the further course macrophages are attracted to them, bind to the constant epitopes of the antibodies take parts of the immune complex by phagocytosis and to build this from.