Cytotoxic T cells

Cytotoxic T cells are a subgroup of T lymphocytes and thus belong to the acquired immune system. Their task is to identify infected cells within the organism and to kill them by the fastest possible means. Like the remaining T-lymphocytes, they are formed in the bone marrow, then migrate into the thymus, where they are finally sorted out again and then develop into mature T-lymphocytes. The cytotoxic T lymphocytes are finally released into the bloodstream, where they finally interact with various endogenous cells and thus check their condition. If an infected or defective cell is involved, the cytoxic T-lymphocytes are able to dock to the MHC molecules of the infected cells via their surface T-cell receptors and kill them by releasing perforin (protein) and granzyme (protease enzyme).

Anti-Human T-Lymphocyte Immunoglobulins

Anti-human T-lymphocyte immunoglobulins are laboratory-produced antibodies that are used as a preventive measure against possible transplant rejection or only after rejection of an already transplanted organ or transplanted stem cells. The reason for the administration of anti-human T-lymphocyte immunoglobulins is that stem cell transplantation occasionally leads to complications. The danger is that the transplant can no longer perform its actual tasks in the foreign body and may attack the recipient body.

The T-lymphocytes play a role in this respect in that they are also introduced into the recipient body by the transplant. The implanted T-lymphocytes now have two effects. On the one hand, they perform their usual task by attacking the infected cells present.

On the other hand, they can trigger the so-called “graft versus host reaction”, since the recipient organism may regard them as foreign and initiate an immune reaction against them. A drug to prevent or treat these reactions has been researched and found in anti-human T-lymphocyte immunoglobulin. This drug is derived from rabbits.

Activation of T lymphocytes

The activation of the T-lymphocytes takes place via an interaction between the T-cell receptors located on the lymphocytes and the matching antigens of the foreign or mutated cells. However, the T-cell receptors can only recognize the antigens if they are presented by so-called antigen-presenting cells.However, other factors are necessary for a stable bond. These include glycoproteins (CD4 and CD8) on the surface of the T lymphocytes and proteins (MHC1 and MHC2) on the surface of the antigen-presenting cell.

It should be noted that the T-helper cells only have CD4 receptors, which in turn can only bind to MHC2 molecules. Accordingly, CD8 receptors can only bind to MHC1 molecules. The CD8-receptors are mainly found on cytotoxic cells, but can also be found on T-killer cells or regulatory T-lymphocytes.

For activation, an antigen-independent co-stimulation is additionally required. It is initiated by surface proteins and starts from the same antigen-presenting cell. After the T-lymphocytes are finally activated, a cellular response can occur.

This consists of the release of various messenger substances, the interleukins, which are subsequently activated by macrophages, T-killer cells or cytotoxic cells. They are then able to eliminate the foreign cells through various cellular mechanisms. In addition, the interleukins can stimulate antibody production so that an increased response to the pathogens can be achieved.