The acquired immune system
The acquired immune system consists of two components: the so-called humoral immune response/immune system, which leads to the formation of antibodies (see below), and the cellular immune response/immune system, which leads to the destruction of the affected pathogen via so-called cytotoxic cells. The lymph cells (lymphocytes) are extremely important for the acquired immune system. Lymphocytes are divided into so-called B and T cells.
The B-cells are activated by complex mechanisms. Thereupon they transform into so-called plasma cells, which are able to produce antibodies against the pathogen. The antibodies are produced specifically against the specific intruder.
They attach themselves to it and can bind it in such a way that, for example, macrophages (scavenger cells) can dock onto the other (still free) side of the antibodies (so-called Fc portion) and then “eat” the “trapped” pathogen. The T cells of the immune system in turn are divided into different cell types with different tasks. On the one hand, there are the so-called cytotoxic (i.e. cell-toxic) T-cells or also called CD8+ cells, which are capable of destroying tumor cells or virus-infected cells.
On the other hand, there are T-helper cells, which are divided into T-helper cells 1 and T-helper cells 2. T-helper cells 1 activate macrophages and dendritic cells (see below). The T-helper cells 2 from the immune system in turn activate antibody formation via the plasma cells (antibody producing B-cells).
The antigen-presenting cells play an enormously important role of the immune system. These are cells that “eat up” pathogens and present their typical proteins to the outside and thus make them recognizable for certain other cells of the immune system (e.g. B cells), whereupon these cells are activated. These antigen-presenting cells of the immune system include B cells, macrophages and the so-called dendritic cells.
These cells can activate T-helper cells 1 and 2 via their presentation ability after they have eaten the pathogens. T helper cells 2 then activate B cells to form antibody-producing plasma cells. T-helper cells 1 activate the scavenger cells.
As mentioned above, the antigen presenting cells already present the major histocompatibility complex (MHC) like all endogenous cells.In addition, however, the recognition protein (antigen) of the pathogen is presented in this complex in these cells. Recently, dendritic cells have been playing an important role in research, as more and more data prove that these cells can have a regulatory effect on both the innate and the acquired immune system. The major histocompatibility complexes (MHC) are very important.
The MHC I are found on every cell in the body that contains a nucleus except nerve cells. The MHC I recognize the cytotoxic (i.e. cell-toxic) T cells mentioned above or CD8+ cells (important for virus and tumor cell defense). The MHC II are located on the antigen presenting cells described above.
They recognize the T-helper cells 2, which activate B-cells to form antibody-producing plasma cells. To ensure that the T-cells do not destroy the body’s own cells, they undergo training in the thymus organ as in school. There a so-called negative selection takes place: When the T cells destroy the body’s own cells, they are sorted out.
