Transplantology

What are the types of transplantation?

The following types of transplantation are distinguished: 

• autotransplantation, or autologous transplantation is a transplantation of an organ within one organism of the same person (the donor and the recipient are one and the same person). For example, autotransplantation of skin from intact areas to the burnt areas in case of severe burns. Autotransplantation of bone marrow or hematopoietic stem cells after high-dose antitumor chemotherapy in leukemia, lymphoma and chemo-sensitive malignant tumors.  
• isotransplantation, or isogenic transplantation – the transplant donor is the recipient’s identical twin who is completely genetically and immunologically identical to the recipient. Such operations are rare, as the number of identical twins is small, besides they often suffer from similar chronic diseases. 
• allotransplantation, or homotransplantation – the transplant donor is a genetically and immunologically non-identical human organism (human-to-human). This is the most used type of transplantation. It is possible to take organs from the recipient’s relatives as well as from other people. 
• xenotransplantation, or inter-species transplantation – organ transplantation from an organism of another biological species (for example, from an animal to a human). This method has been applied to an extremely limited extend (use of xeno-skin – pig skin, cell culture of pig’s pancreas β-cells). 

What medical cases require a transplant operation?

A transplant operation is needed in case when an organ or a part of body loses the capability to perform its functions. This may be caused by a congenital abnormality, a disease or a serious trauma, intoxication (liver transplantation). Fire victims often get transplanted their own intact skin on the burnt areas.  

What are the medical requirements for carrying out of a living-donor transplantation? 

Donor’s and recipient’s health 

• One of the paired organs, a part of an organ and tissue, missing of which won’t produce irreversible health disorders, can be taken for transplantation from a living donor. Besides, the transplanted organs are to be intact, healthy and physiologically properly functioning.    
• Stable condition of the recipient before the operation. 

Compatibility of donor and recipient 

Before the operation, the donor and recipient immune system data is carefully studied and compared to establish compatibility to prevent a rejection reaction and other possible complications. 

Currently, donor selection is performed based on two main antigen systems: 

• Compatibility according to the AB0 system (erythrocyte antigens). When transplanting organs an optimal matching of donor’s and recipient’s blood group according to the AB0 system is important. Incompatibility according to the AB0 system is also acceptable.  
• Compatibility according to the HLA system (leucocyte antigens, known as histocompatibility antigens) 
• HLA antigens compatibility is considered to be determinative when selecting a donor.  

What a rejection reaction means

Rejection is an inflammatory affection of a transplanted organ (transplant) caused by a specific response of the recipient’s immune system to the donor’s transplantation antigens. 

Despite the measures taken to select the most genetically congenial donor for each recipient, it is not possible to achieve a complete genotype identity; recipients may experience a rejection reaction after operations. When performing autotransplantation operations, in case when the donor and the recipient are one and the same person, the danger of a rejection reaction is rare. The more compatible the recipient and the donor are, the less frequently the rejection occurs. 

How are the rejection reactions prevented? 

Immunosuppression 

To prevent organ rejection after transplantation, a pharmacological/medical immunosuppression is performed in the recipient to reduce the efficacy of the immune system. In a noncomplicated progress, relatively small doses of drugs are used according to special schedules. In case of graft-versus-host disease progress, the dosage of immunosuppressive agents is significantly increased, their combination is changed.     

The patients should remember that the immunosuppression leads to a significant increase of risk of infectious postoperative complications.

The natural rejection reactions, occurring in human body after transplantation, are suppressed by drugs. The patient, whom an organ had been transplanted in, will remain under physician’s care for the rest of his life.     

What are the organs and tissues that can be transplanted?
 

İt is theoretically possible to transplant any organ. But in fact, the possibilities are limited. Nowadays only some types of organs are transplantable and make possible transplant operations to be performed.

• Kidney transplantation 
• Liver transplantation 
• Heart transplantation 
• Pancreas transplantation
• Bone marrow transplantation
• Skin transplantation
• Lung transplantation 

Currently the organ transplantation of liver, kidney, heart, lung and pancreas is performed, as well as endocrine glands’ tissue and cell cultures transplantation, bone marrow transplantation.