Tissue incompatibility is a complex of the body’s immune responses to transplanted foreign cells, tissues or organs. Tissue incompatibility arose in the process of evolution as the development of a body's defensive reaction against bacteria and other alien biological agents. The basis of tissue incompatibility are the phenomena of immunity (see). Tissue incompatibility is observed with various types of transplants of organs and tissues (see). In the case of hetero- or xenotransplantation (transplantation of an organ from another species of animal), the main cause of incompatibility is the species differences of the donor and recipient organisms. When homo-or allotransplantation (transplantation of organs from an animal of the same species or from person to person), tissue incompatibility is due to the individual characteristics of the specificity of proteins, polysaccharides and cell lipids. These features are due to the presence in all tissues of the body of various antigens (see).
The body acquires antigenic properties already in the early stages of prenatal development , therefore, the transplantation of embryonic tissues is also accompanied by tissue incompatibility, but in some cases it is less pronounced.Go
The reaction aimed at rejection of the transplant causes its death in a few weeks or even days. This reaction depends on the activity of immunocompetent lymphocytes reacting to the graft as an alien protein. As a result, infiltration of the graft with lymphoid cells occurs and cessation of blood flow in it. Starting locally, this reaction gradually assumes a generalized character and leads to rejection of the transplanted organ.
Therefore, in experimental and clinical transplantations of donor tissue, it is necessary to take appropriate measures in order to reduce the incompatibility reaction. These measures are carried out in two main directions. The first of these is donor selection. It is obvious that the smallest immunological differences will have those donor-recipient pairs, in which not only the specific specificity is excluded, but also the individual is minimized. Such pairs are either brothers and sisters (primarily identical twins), or parents and children, but this does not exclude the coincidence of different antigens from unrelated couples. At present, the selection of a donor-recipient pair is made by comparing their transplantation antigens. The second direction in the fight against tissue incompatibility is its suppression by various physical or pharmacological means. These include surgical removal of lymphoid organs from the recipient, primarily those responsible for immunological reactions (thymus, spleen, regional lymph nodes), the use of drugs that suppress the immune response, etc. However, it must be remembered that these measures time sharply reduces the body's resistance to various infections, since both reactions — tissue incompatibility and protection against infectious influences — are based on the same immunological mechanisms.