Transplantation: Definition, Types, Mechanism, Prevention of Rejection & Organ Banks

Transplantation: Your body can regenerate damaged skin cells; a first-degree or superficial burn heals normally. What if there are deep second and full-thickness burns? In this scenario, skin graft surgery is essential. In the same way, if an organ fails, it can be replaced by a healthy organ through transplantation. A transplant is a procedure in which a part of a tissue or an entire organ is removed from its natural position and transplanted to a new location in the same or other individuals. Read on more to understand transplantation and its definition, types, mechanism, prevention of rejection & organ banks.

Definition of Transplantation

Transplantation is a surgical operation in which tissue or an organ is moved from one part of a person’s body to another or from one person (the donor) to another (the recipient). It is commonly known that an animal will take grafts of its own tissue or that of an identical twin but will reject grafts from another animal of the same species. Exogenous graft rejection is caused by an immune response triggered by transplantation (HLA) antigens found in all mammalian cells. Sushrut Sanhita offers the first record of plastic surgery (800 BC). Sushruta, the first Indian surgeon, used the patient’s own skin flap to repair a severed nose.

Types of Transplantation

(a) Auto-graft
A transplant of tissue or whole organ from one part of the body to another part of the same animal is called autograft.
(b) Isograft
It is a graft implanted in another person with the same genetic makeup (e.g. monozygous twins or members of inbred strains) when one identical twin and the other identical twin are transplanted.
(c) Allograft or Homograft
It’s a graft between two members of the same species that are genetically diverse.
(d) Xenograft
Xeno-grafts are grafts between individuals of different species. It was formerly known as heterograft.

Auto-grafts and isografts are commonly accepted, and the body survives with the minimum inflammatory response. Because of genetic and antigenic incompatibility, allografts and xenografts frequently necrotise and are rejected.

Need for Transplantation

1. Patients with terminal organ failures benefit from solid organ transplants because they save their lives and improve their quality of life.
2. Patients with congenital diseases can undergo transplantation and have a better life.
3. Organ transplantation has steadily improved over the last two decades, and it now produces good results in adolescents and young adults.
4. In the circumstances like accidents or injuries that cause tissue or organ failure, they could be saved by organ or tissue transplantation
5. Renal transplantation improves patients’ survival over dialysis, and lifesaving transplants are required to treat patients with irreversible illnesses of the liver, heart, or lungs.
6. The number of solid organ transplant programmes has been continuously increasing, but it still falls short of worldwide needs, with significant variances between nations.

Criteria for Healthy Transplantation

1. The severity of the patient’s condition is checked before transplantation.
2. The organ donor’s history of TB and chronic illnesses like HIV is checked.
3. The overall physical condition & mental well-being of donor and recipient should be taken into consideration.
4. Alcohol abuse & smoking makes the donor unhealthy to donate an organ.
5. Overdose of acetaminophen- Renal failure can result from acetaminophen-induced organ harm, which can occur with or without hepatotoxicity, complicating the evaluation of such donors.
6. Obesity- Most patients with a BMI of 35 or more are considered ineligible to donate, and the majority of transplant hospitals refuse to accept these obese living donors.

Types of Organs that are Transplanted

Fig: Organs Transplantation

Organ transplantation is a medical technique that involves removing an organ from one body and transplanting it into the body of another to replace a damaged or missing organ. Organs that can be transplanted include the following:

1. Heart
2. Intestine
3. Kidney
4. Liver
5. Lung
6. Pancreas

Of all the organs transplanted, the lungs are the most difficult. The process is complicated because the lungs are situated inside the rib cage and chest wall, and the donor and recipient must have similar physical measurements, or the lungs will not fit. Then there’s primary lung graft dysfunction, or PGD, which is a common complication following a lung transplant. This occurs within the first 72 hours of a successful transplant and is characterised by significant swelling and insufficient oxygenation of the new lungs. In 10 to 25% of all lung transplant operations, PGD occurs.

Fig: Nose Surgery

Mechanism of Transplantation Rejection

Allograft Reaction

Allograft response refers to the recipient’s rejection of the graft. Graft rejection occurs when the recipient’s immune system rejects the given tissue or organ and begins to destroy it. The presence of the donor’s own unique set of HLA proteins, which the recipient’s immune system recognises as foreign substances, frequently triggers the immunological response. A kidney transplant is the most successful organ transplant. Other organ transplants, such as bone marrow, have also been attempted but with little success.

Changes seen in human renal allograft rejection are nearly identical to those seen in mice:

1. Within a few days, the graft gets vascularised and appears to be accepted.
2. Between 3 and 9 days, lymphocytes and monocytes infiltrate the graft, resulting in a significant reduction in circulation. Only a few plasma cells have invaded the graft at this point.
3. The necrosis becomes obvious to the naked eye after 10-11 days.
4. The graft sloughs off completely on the 12th or 13th day.
5. The rejection is almost entirely due to the cell-mediated reaction.
6. Helper T cells activate cytotoxic T cells, macrophages, and B cells, causing a second allograft from the same donor to be rejected in 5-6 days when given to a sensitised recipient. Antibodies, together with cell-mediated immunity, play a crucial role in the rapid rejection of second graft second set reaction.
7. Antibodies start to build in large quantities after the 11th day following transplantation. As a result, either sensitised T cells or circulating antibodies reject the graft.
8. Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) causes platelet aggregation or type II hypersensitivity reaction.

Tissue Typing and Matching in Transplantation

Tissue typing is a method that tests the compatibility of a potential donor’s and recipient’s tissues before transplantation. Tissue rejection can occur when donor and recipient tissues are mismatched. All tissue transplantation requires ABO compatibility. HLA compatibility is essential for an allograft’s survival. An individual’s entire HLA type is made up of two haplotypes (one strand of chromosomal pair) inherited from each parent.

A decent likelihood of genetic matching of a patient’s siblings exists, with a 25% chance for both haplotypes and a 50% chance for one haplotype. With so many HLA antigens revealed, a thousand halo-types are possible. There’s a rare chance that two persons with identical haplotypes may cross paths. As a result, family members are chosen as the best HLA compatible donors.

1. Leucocytes Grouping

The following sources are used to identify HLA antigens on leucocytes of the class I type:

1. Multiparous women who usually have antibodies to their spouses’ HLA antigens
2. Multiple blood transfusion of recipient
3. Volunteers who get their skin grafted regularly.
4. HLA antigen-specific monoclonal antibodies

2. Mixed Leucocyte Culture Test

The test detects HLA complex class II antigens as well as cell-mediated immunity. Both donors and recipients’ lymphocytes are grown together (co-cultivation). The test is built on the concept that T-lymphocytes undergo blastoid transformation, take up thymidine, and divide when exposed to incompatible HLA antigen.

3. Lymphocyte Transfer Test

The recipient’s peripheral blood lymphocytes are injected intradermally into multiple potential donors. The immunological response of recipient leucocytes to the donor tissue is indicated by a delayed hypersensitivity reaction at the injection site. Donors are chosen based on their lack of reaction to the recipient’s leucocytes.

4. Detection of Preformed Antibody

The lymphocytes of the donor are matched to the serum of the receiver. The donor’s lymphocytes are lysed if pre-existing antibodies are present in the patient’s serum.

Prevention of Graft Rejection in Transplantation

1. Immunosuppression

When the HLA type of the recipient and donor are well-matched, the recipient develops immunosuppression by inducing drugs, which allows the transplanted tissue to survive for a long time. Immunological reactivity can be decreased non-specifically by irradiation, corticosteroids, and anti-lymphocytic serum (ALS).

2. Transplantation in Anatomically Protected Sites

Allografts are allowed to survive in specific anatomically protected areas, such as the cornea, cartilage, and testicle transplanting. The cornea’s avascularity prevents lymphocytes from entering the transplant.

3. Immunological Enhancement
   1. Under certain conditions, circulating antibodies against graft antigens can protect the graft from the cell-mediated immune response. This is known as Immunological enhancement.
   2. The transplant survives longer if the recipient animal has been immunised with one or more tissue injections from the prospective donor before the transplant is performed.
   3. The graft retains normal function for a year or more after transplantation of kidneys in rats using this procedure.
   4. An immunised animal’s immunological superiority can be passively transferred to a non-immunised animal.
   5. The procedure has been employed in certain human kidney transplantations.

Organ and Tissue Banks

1. Without a blood supply, organs deteriorate rapidly. Cooling can slow down but not stop the process. The susceptibility of different organs to injury varies.
2. The brain is irreversibly destroyed in 3 to 5 minutes at normal body temperature; the heart, liver, pancreas, and lung in 10 to 30 minutes; the kidney in 50 to 100 minutes; and the skin and cornea in 6 to 12 hours.
3. The less time the organ is cut off from its blood supply, the better. Although the cornea can be removed at a leisurely pace for grafting, every minute counts in a liver transplant.
4. It is not required to apply complicated preservation measures when removing a kidney from a living donor.
5. The donor and recipient organs are operated on simultaneously, and the recipient is ready to accept the graft by the time the donor organ is removed.
6. Cadaver kidneys are removed as soon as the donor dies, preferably within an hour.
7. Cool solutions, stored at 4 °C (39 °F) in the refrigerator or covered by ice in a vacuum flask, are injected into the kidney’s blood arteries.
8. Kidneys may be preserved in this manner for 24 to 48 hours with negligible degeneration, and they can be transported over long distances during this time.

Summary

A transplant is a procedure in which a piece of tissue or an entire organ is removed from its natural position and transplanted to a new location in the same or other individuals. This surgical method is called transplantation. There are various types of transplantation, such as autografts, xenografts, isografts. Allograft response refers to the recipient’s rejection of the graft. A kidney transplant is the most successful organ transplant. Tissue typing and matching in transplantation are of various types, such as leucocytes grouping, lymphocyte transfer test, mixed leucocyte culture test, and detection of preformed antibody. Prevention of Graft Rejection in transplantation can be done in many ways, such as Immunosuppression, Transplantation in Anatomically Protected Sites and Immunological Enhancement and maintaining organ and tissue banks.

Frequently Asked Questions (FAQs) on Transplantation

Q.1. What do you mean by transplantation?
Ans: A surgical technique that involves the transfer of tissue or an organ from one part of a person’s body to another or from one person (the donor) to another (the recipient).

Q.2. What is the reason for transplantation?
Ans: Because of a genetic disorder like polycystic kidney disease, cystic fibrosis, or a heart problem, many people require an organ transplant. Infections like hepatitis, physical trauma to organs, and damage caused by chronic diseases like diabetes can all lead to the need for a transplant.

Q.3. What is the hardest organ to transplant?
Ans: Of all the organs transplanted, the lungs are the most difficult. The process is complicated because the lungs are situated inside the rib cage and chest wall, and the donor and recipient must have similar physical measurements, or the lungs will not fit.

Q.4. What are the drawbacks of transplantation?
Ans: Transplantation is a significant surgical procedure that is fraught with dangers both before and after the procedure. Infection, haemorrhage, and organ damage are all possible side effects of the surgery. Death is a possibility, but it is extremely uncommon.

Q.5. What was the first human transplant?
Ans: The kidney became the first successful human organ transplant in 1954. By the 1960s, liver, heart, and pancreatic transplants had proven to be successful, whereas lung and intestinal organ transplants had only recently been available.

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