Allograft Health Dictionary

A piece of tissue or an organ, such as a kidney, transplanted from one animal to another of the same species: for example, from person to person. It is also known as an allograft.... homograft

The process of transplanting healthy tissue from one part of the body to another (autografting), from one person to another (allografting), or from an animal to a person (xenografting).

Grafting is used to repair or replace diseased, damaged, or defective tissues or organs. The most common operations of this type are skin graft, bone graft, bone marrow transplant, corneal graft, kidney transplant, heart transplant, liver transplant, heart–lung transplant, heartvalve surgery, and microsurgery on blood vessels and nerves.

With autografting, the grafted tissue is usually assimilated well into the surrounding tissue at the new site.

The general risks of tissue rejection following other forms of grafting are discussed in transplant surgery.... grafting

n. a tissue graft taken from one part of the body and transferred to another part of the same individual. The repair of burns is often done by grafting on strips of skin taken from elsewhere on the body, usually the upper arm or thigh. Unlike *allografts, autografts are not rejected by the body’s immunity defences. See also skin graft; transplantation.... autograft

the use of bone or a bonelike synthetic substance to fill a bony defect or to augment bone formation. Bone grafts are usually *autografts or *allografts, but synthetic bone grafts, using calcium compounds and hydroxyapatite, are increasingly being used. Hard cortical bone can be used to replace structural defects, softer cancellous bone is used to fill voids or to encourage bony union, and synthetic bone grafts act as a scaffold through which normal bony healing can occur.... bone graft

a type of T *lymphocyte that destroys cancerous cells, virus-infected cells, and *allografts. Cytotoxic T cells recognize peptide antigens attached to proteins that are encoded by the *HLA system.... cytotoxic t cell

1. n. any organ, tissue, or object used for *transplantation to replace a faulty part of the body. A *skin graft is used to heal a damaged area of skin. A *bone graft can be performed using natural bone or a synthetic material. A kidney removed from a live or dead person and transplanted to another individual is described as a kidney (or renal) graft. Corneal grafts are taken from a recently dead individual to repair corneal opacity (see keratoplasty). Diseased coronary arteries may be replaced by a *coronary artery bypass graft. Artificial grafts are used to replace diseased peripheral arteries and heart valves. 2. vb. to transplant an organ or tissue. See also allograft; xenograft.... graft

n. (in transplantation) the destruction by immune mechanisms of a tissue grafted from another individual. Antibodies, complement, clotting factors, and platelets are involved in the failure of the graft to survive. *Allograft rejection is a vigorous response that can be modified by drugs (such as ciclosporin and corticosteroids) and antibodies against T cells; *xenograft rejection is an acute response that is at present beyond therapeutic control.... rejection

a portion of healthy skin cut from one area of the body and used to cover a part that has lost its skin, usually as a result of injury, burns, or operation. A skin graft is normally taken from another part of the body of the same patient (an *autograft), but occasionally skin may be grafted from one person to another as a temporary healing measure (an *allograft). The full thickness of skin may be taken for a graft (see flap) or the surgeon may use three-quarters thickness, thin sheets of skin (see split-skin graft), or a pinch skin graft. The type used depends on the condition and size of the damaged area. The skin graft may be free or attached by a *pedicle.... skin graft

n. the implantation of an organ or tissue (see graft) from one part of the body to another or from one person (the donor) to another (the recipient). Success for transplantation depends on the degree of compatibility between donor and graft: it is greatest for *autografts (self-grafts), less for *allografts (between individuals of the same species), and least for *xenografts (between different species; see xenotransplantation). Skin and bone grafting are examples of transplantation techniques in the same individual. A kidney transplant involves the grafting of a healthy kidney from a donor to replace the diseased kidney of the recipient: renal transplantation is the second commonest example of human transplant surgery using allografts (after corneal grafts – see keratoplasty). Bone-marrow, blood-stem-cell, heart, heart–lung, pancreatic, and liver transplants are also very successful. Patients have undergone laryngeal transplantation following *laryngectomy. Transplanting organs or tissues between individuals is a difficult procedure because the recipient’s immune system perceives the transplant as a foreign object and rejects it. Special treatment (e.g. with *immunosuppressant drugs) is needed to prevent transplant rejection, and the less common but equally devastating effects of an attack by the graft’s immune cells on the host.

Ethical questions arise over donated organs. If the donor is living, is the organ properly a *gift? If the donor has recently died, how has the death been judged and has *consent been given explicitly by the patient or surviving relatives (opting in) or is it assumed if the donor has not forbidden it (opting out)?... transplantation