Instruct: Given a question, retrieve relevant documents that answer the question.
Query: What does transplant rejection mean?
Transplant rejection occurs when transplanted tissue is rejected by the recipient's immune system, which destroys the transplanted tissue. Transplant rejection can be lessened by determining the molecular similitude between donor and recipient and by use of immunosuppressant drugs after transplant.[1]
An allograft is a transplant of an organ or tissue between two genetically non-identical members of the same species. Most human tissue and organ transplants are allografts. Due to the genetic difference between the organ and the recipient, the recipient's immune system will identify the organ as foreign and attempt to destroy it, causing transplant rejection. The risk of transplant rejection can be estimated by measuring the Panel reactive antibody level.
Overseas employment has improved the standard of living without prejudice to the inbred unwritten tribal code and tenacious adherence to it. Development for them does not mean a wholesale rejection of traditions. Wholesale transplanting of innovations into a tribal society could not overcome the ferocious power of tradition; it is essential to graft these innovations only after first making the environment congenial and receptive.
In his paper, "Content Ex Machina" Bach argues against over-interpreting what he labels the "contextualist platitude" which he defines as: “Generally what a speaker means in uttering a sentence, even if the sentence is devoid of ambiguity, vagueness, or indexicality, goes beyond what the sentence means.” Bach asserts that context does not establish meaning but is merely one of several conversational principles. He states that “context does not determine (in the sense of constitute), but merely enables the hearer to determine (in the sense of ascertain) what the speaker means.” Context provides constraints on what a speaker can reasonably mean and on what a hearer can reasonably interpret a speaker to mean. “contextualist platitude” does not preclude the “older picture of language and communication” and “a fairly standard semantic-pragmatic distinction.” Pragmatic considerations and context do not contribute to the content of what is said. Bach admits that there is meaning in utterances beyond the semantic content of a sentence, but he maintains that context does not determine speaker meaning but rather constrains how a speaker can expect to be understood and helps the hearer understand what is said. “We need the level of locutionary act and, correlatively, a strict, semantic notion of what is said in order to account for (the content of) what a speaker does in uttering a sentence independently of whatever communicative intention (if any) he has in uttering it and regardless of how the content of that intention may depart from the semantic content of the sentence.” 
ABO-incompatible (ABOi) transplantation is a method of allocation in organ transplantation that permits more efficient use of available organs regardless of ABO blood type, which would otherwise be unavailable due to hyperacute rejection. Primarily in use in infants and young toddlers, research is ongoing to allow for increased use of this capability in adult transplants. Normal ABO-compatibility rules may be observed for all recipients. This means that anyone may receive a transplant of a type-O organ, and consequently, type-O recipients are one of the biggest beneficiaries of ABO-incompatible transplants. While focus has been on infant heart transplants, the principles generally apply to other forms of solid organ transplantation.
Kountz completed a master's degree in chemistry in 1956; two years later he received his M.D. He spent the next year as an intern with the highly competitive Stanford Service of San Francisco General Hospital, and, in 1959, he began his surgical training at the Stanford University School of Medicine. It was at Stanford that he studied the field of organ transplantation, and decided to make transplant surgery his life's work. He was still a resident in 1961, when he made medical history by performing the first kidney transplant using a non-twin donor. Among Kountz's other contributions were the discovery that large doses of the steroid drug methylprednisolone could reverse acute rejection of a transplanted kidney, and that re-implantation (the implantation of a second donor kidney at the earliest indication that the first might be rejected) could mean the difference between the death and survival for transplant patients. A tireless proponent of organ donation, he once performed a kidney transplant on live television, The Today Show, in 1976, inspiring some 20,000 viewers to offer their kidneys to patients who needed them. In addition, his groundbreaking research in the area of tissue typing helped improve the results of kidney transplantation and led to the increased use of kidneys from unrelated donors.
After passing his exam, Woodruff entered his position at Sheffield, where he trained in emergency and elective surgery. Originally, he had planned to do surgical research, but Sheffield had no space for him in its surgical lab. Instead, Woodruff was given a place in the pathology laboratory where he studied transplant rejection, a process in which the immune system of a transplant recipient attacks the transplanted tissue. Woodruff was particularly interested in thyroid allografts to the anterior chamber of the eye because they did not appear to meet with rejection. Woodruff's work with the allografts gave him a solid basis to work in the developing field of transplantion and rejection. To further himself in these areas, Woodruff arranged to meet Peter Medawar, an eminent zoologist and important pioneer in the study of rejection. The two men discussed transplantation and rejection, beginning a lasting professional relationship. Despite his achievements at Sheffield, Woodruff was rejected upon applying for a post at the Royal Melbourne Hospital.
Hyperacute rejection manifests severely and within minutes, and so treatment is immediate: removal of the tissue. Chronic rejection is generally considered irreversible and poorly amenable to treatment—only retransplant generally indicated if feasible—though inhaled ciclosporin is being investigated to delay or prevent chronic rejection of lung transplants. Acute rejection is treated with one or several of a few strategies. Despite treatment, rejection remains a major cause of transplant failure.[26]
In the USA, corneal transplants (also known as corneal grafts) for keratoconus are usually performed under sedation as outpatient surgery. In other countries, such as Australia and the UK, the operation is commonly performed with the person undergoing a general anaesthetic. All cases require a careful follow-up with an eye doctor (ophthalmologist or optometrist) for a number of years. Frequently, vision is greatly improved after the surgery, but even if the actual visual acuity does not improve, because the cornea is a more normal shape after the healing is completed, people can more easily be fitted with corrective lenses. Complications of corneal transplants are mostly related to vascularization of the corneal tissue and rejection of the donor cornea. Vision loss is very rare, though difficult-to-correct vision is possible. When rejection is severe, repeat transplants are often attempted, and are frequently successful. Keratoconus will not normally reoccur in the transplanted cornea; incidences of this have been observed, but are usually attributed to incomplete excision of the original cornea or inadequate screening of the donor tissue. The long-term outlook for corneal transplants performed for keratoconus is usually favorable once the initial healing period is completed and a few years have elapsed without problems.
Transplant rejection is a primary concern, both immediately after the surgery and continuing throughout the patient's life. Because the transplanted lung or lungs come from another person, the recipient's immune system will see it as an invader and attempt to neutralize it. Transplant rejection is a serious condition and must be treated as soon as possible.
Developing with formation of cellular immunity, acute rejection occurs to some degree in all transplants, except between identical twins, unless immunosuppression is achieved (usually through drugs). Acute rejection begins as early as one week after transplant, the risk being highest in the first three months, though it can occur months to years later. Highly vascular tissues such as kidney or liver often host the earliest signs—particularly at endothelial cells lining blood vessels—though it eventually occurs in roughly 10 to 30% of liver transplants, and 10 to 20% of kidney transplants. A single episode of acute rejection can be recognized and promptly treated, usually preventing organ failure, but recurrent episodes lead to chronic rejection. It is believed that the process of acute rejection is mediated by the cell mediated pathway, specifically by mononuclear macrophages and T-lymphocytes.
Post-operative complications include infection, sepsis, organ rejection as well as the side-effects of the immunosuppressive medication. Since the transplanted heart originates from another organism, the recipient's immune system typically attempts to reject it. The risk of rejection never fully goes away, and the patient will be on immunosuppressive drugs for the rest of their life, but these may cause unwanted side effects, such as increased likelihood of infections or development of certain cancers. Recipients can acquire kidney disease from a heart transplant due to side effects of immunosuppressant medications. Many recent advances in reducing complications due to tissue rejection stem from mouse heart transplant procedures. The surgery death rate was 5–10% in 2011.
Let me be clear about what affirmative action must not mean and what I won't allow it to be. It does not mean – and I don't favor – the unjustified preference of the unqualified over the qualified of any race or gender. It doesn't mean – and I don't favor – numerical quotas. It doesn't mean – and I don't favor – rejection or selection of any employee or student solely on the basis of race or gender without regard to merit…
Mycophenolate is used for the prevention of organ transplant rejection. Mycophenolate mofetil is indicated for the prevention of organ transplant rejection in adults and renal transplant rejection in children over 2 years; whereas mycophenolate sodium is indicated for the prevention of renal transplant rejection in adults. Mycophenolate sodium has also been used for the prevention of rejection in liver, heart, or lung transplants in children older than two years. It is also used for retroperitoneal fibrosis along with a number of other medications.
Of these challenges, dealing with blood supply and transplant rejection have been addressed in the field of transplant medicine generally, making transplantation of several types of organs fairly routine; however in a field as common as liver transplantation around a quarter of organs are rejected within the first year and overall mortality is still much higher than the general population. The challenge of grafting the nervous system remained in early stages of research .
Transplant glomerulopathy, abbreviated TG, is a disease of the glomeruli in transplanted kidneys. It is a type of renal injury often associated with chronic antibody-mediated rejection. However, transplant glomerulopathy is not specific for chronic antibody-mediated rejection; it may be the result of a number of disease processes affecting the glomerular endothelium.
A clinical moratorium on heart transplants in the UK was announced by Sir George Godber, Chief Medical Officer (United Kingdom) in February 1973. This was a result of poor results in most units around the world during the years following Christiaan Barnard's first transplant in December 1967 apart from Stanford University's in California where Norman Shumway had pioneered heart transplantation and Barnard's unit in Cape Town. It was felt at the time that cardiac transplantation required more research into the management of rejection, more donors and a change in public opinion. Three months after the moratorium on heart transplantation, English became inspired by a visit to his friend Philip Caves, at Stanford University, who had developed the technique of transvenous myocardial biopsy to detect acute organ rejection at an early stage, and was then Chief Resident in Shumway's unit. Caves had been working with pathologist Margaret Billingham, who devised the scoring system for early rejection. This advance and better knowledge of how to use drugs for immunosuppression had led to significant improvement in results at Stanford he decided that it was time for the UK to have its own programme of heart transplantation, based on what he had seen there. So in October 1973 formal meetings began between surgical colleagues at Papworth and Sir Roy Calne at Addenbrooke's where there was already an active programme of kidney and liver transplantation. In preparation for this English did some open heart surgery at Addenbrooke's Hospital and also became involved with Roy Calne's pig heart transplant research.
Many other new drugs are under development for transplantation.
The emerging field of regenerative medicine promises to solve the problem of organ transplant rejection by regrowing organs in the lab, using person's own cells (stem cells or healthy cells extracted from the donor site).From year 2000 and forward, there have been approximately 2,200 lung transplants performed each year worldwide. From between 2000 and 2006, the median survival period for lung transplant patients has been 5-and-a-half years, meaning half the patients survived for a shorter time period and half survived for a longer period.
The brain was thought to be an immunologically privileged organ, so rejection would not be a problem. (When other organs are transplanted, aggressive rejection can occur; this is a major difficulty with kidney and liver transplants. Immune cells of the CNS contribute to the maintenance of neurogenesis and spatial learning abilities in adulthood, so the transplanted brain would not be unhindered from the transplant.)
Hyland was diagnosed with kidney dysplasia as a young child and received a kidney transplant from her father in April 2012. That kidney failed after a few years, leading to a second kidney transplant in September 2017, donated by her younger brother, Ian. Hyland is on regular anti-rejection medicines and steroids to ensure that her body does not reject her donated kidney. Consequently, Hyland has difficulty maintaining weight and muscle mass, and has been put on bed-rest several times, sometimes continuing to film "Modern Family" simultaneously.
The term chronic rejection initially described long-term loss of function in transplanted organs via fibrosis of the transplanted tissue's blood vessels. This is now chronic allograft vasculopathy, however, leaving chronic rejection referring to rejection due to more patent aspects of immunity.
Some studies seem to suggest that the longer a patient is on dialysis before the transplant, the less time the kidney will last. It is not clear why this occurs, but it underscores the need for rapid referral to a transplant program. Ideally, a kidney transplant should be pre-emptive, i.e., take place before the patient begins dialysis. The reason why kidneys fail over time after transplantation has been elucidated in recent years. Apart from recurrence of the original kidney disease, also rejection (mainly antibody-mediated rejection) and progressive scarring (multifactorial) play a decisive role. Avoiding rejection by strict medication adherence is of utmost importance to avoid failure of the kidney transplant.
René Küss (3 May 1913 – 2006) was a French pioneering urologist and transplant surgeon who made ground-breaking contributions in renal tract surgery and kidney transplantation with the establishment of transplant programs. At a time of unavoidable transplant rejection, he was involved in two particularly historic transplant operations. The first was a human-to-human extraperitoneal kidney transplant procedure in 1951 and later a pig-to-human kidney transplant in 1966, both of which ended in abrupt rejection. He later introduced kidney transplantation schedules involving at first irradiation, later immunosuppressants, living-related and unrelated donors and later organs from deceased donors.
Recently, researchers have been looking into means of reducing the general burden of immunosuppression. Common approaches include avoidance of steroids, reduced exposure to calcineurin inhibitors, and other means of weaning drugs based on patient outcome and function. While short-term outcomes appear promising, long-term outcomes are still unknown, and in general, reduced immunosuppression increases the risk of rejection and decreases the risk of infection. The risk of early rejection is increased if corticosteroid immunosuppression are avoided or withdrawn after renal transplantation.
Transplantation medicine is one of the most challenging and complex areas of modern medicine. Some of the key areas for medical management are the problems of transplant rejection, during which the body has an immune response to the transplanted organ, possibly leading to transplant failure and the need to immediately remove the organ from the recipient. When possible, transplant rejection can be reduced through serotyping to determine the most appropriate donor-recipient match and through the use of immunosuppressant drugs.