A transplant is a medical procedure that moves a healthy organ, tissue, or group of cells from one body (or one part of a body) to another to replace something that is diseased or failing. In 2024, a record 173,727 solid organ transplants were performed worldwide, with the United States alone accounting for 48,935 of them. Transplants range from common procedures like kidney replacements to complex operations involving the heart, lungs, or even the face and hands.
What Can Be Transplanted
The list of transplantable body parts is longer than most people expect. Eight organs can be transplanted from a deceased donor: kidneys, liver, lungs, heart, pancreas, intestines, hands, and face. Because we have paired organs and the liver can regenerate, living donors can give one kidney, one lung, or a portion of the liver, pancreas, or intestine.
Beyond whole organs, tissue transplants are extremely common. Tissue banks store corneas, skin, heart valves, bone, cartilage, tendons, ligaments, veins, and middle ear structures. These tissues can restore sight, rebuild damaged joints, repair burns, and fix heart defects. A single deceased donor can provide organs and tissues that help dozens of recipients.
Stem cell transplants (sometimes called bone marrow transplants) are a distinct category. Instead of replacing a structural organ, they replenish the blood-forming cells inside your bones. Stem cells can come from bone marrow, umbilical cord blood collected at birth, or circulating blood after a donor receives injections that push stem cells out of the marrow. These transplants treat blood cancers like leukemia and lymphoma, genetic conditions like sickle cell disease and thalassemia, immune deficiency disorders, and even some autoimmune diseases such as multiple sclerosis.
Living vs. Deceased Donors
Organs come from two sources. A living donor voluntarily gives an organ or part of one while alive. To qualify, living donors must be at least 18 (some hospitals require 21), be in good physical and mental health, and make an informed decision after understanding the risks. Living donors can also give skin after certain surgeries, bone removed during hip or knee replacements, blood, platelets, and amnion tissue donated after childbirth.
Deceased donors are people who have died, typically from brain death or cardiac death, and whose organs are recovered for transplant. A single deceased donor can provide up to eight organs plus a wide range of tissues. Because demand far exceeds supply, national allocation systems determine who receives an available organ.
How Organs Are Matched to Recipients
Matching a donor organ to a recipient involves several biological tests. Blood type compatibility is the first filter. Next, doctors examine human leukocyte antigens (HLA), a set of proteins on cell surfaces that your immune system uses to distinguish “self” from “foreign.” The closer the HLA match between donor and recipient, the lower the risk of rejection. Recipients are also screened for antibodies that might attack a donor’s tissue. If preexisting antibodies target the donor’s HLA markers, that donor is typically ruled out.
In the United States, each organ has its own allocation scoring system. Liver allocation uses a score based on blood tests that estimate how urgently a patient needs a transplant to survive. Kidney allocation weighs both donor quality and recipient factors like age, diabetes status, and time spent on dialysis to maximize the organ’s useful life. Lung allocation balances how likely a patient is to die on the waitlist against how likely they are to survive after surgery. Heart allocation uses a six-tier urgency system based on what level of medical support the patient currently needs, with the most critically ill patients ranked highest.
How Your Body Responds to a New Organ
Your immune system is designed to attack anything it doesn’t recognize, and a transplanted organ from another person carries foreign markers. This immune response is called rejection, and it can happen in several ways depending on the timing.
Hyperacute rejection is the fastest form, occurring within minutes of transplantation. It happens when a recipient already has antibodies against the donor’s tissue, triggering rapid blood clotting inside the new organ’s vessels. Modern crossmatch testing has made this rare. Acute rejection develops over days to weeks and involves your immune system’s T cells and B cells mounting a targeted attack against the transplanted tissue. This is the type doctors watch for most closely in the early months after surgery. Chronic rejection unfolds over months or years as ongoing low-level immune activity gradually damages the organ, eventually reducing its function.
To prevent these responses, transplant recipients take immunosuppressive medications for as long as they have the organ. These drugs dial down immune activity enough to protect the transplant but not so much that the body can’t fight infections. The tradeoff is real: long-term immunosuppression raises the risk of infections and certain cancers, and the medications themselves can cause side effects like high blood pressure, kidney strain, tremors, elevated cholesterol, and weight gain. Doctors adjust dosages over time, typically using higher doses in the early months when rejection risk peaks, then tapering to the lowest effective level.
Types of Grafts
Not every transplant involves moving tissue between two different people. Surgeons classify grafts by the relationship between donor and recipient. An autograft uses your own tissue, moved from one site to another, like taking skin from your thigh to cover a burn on your arm or harvesting bone from your hip to rebuild your jaw. Because the tissue is yours, there’s no rejection risk, making autografts the gold standard when possible.
An allograft comes from another person of the same species. This covers the vast majority of organ transplants, from kidneys to hearts. Allografts require careful screening, processing, and immune suppression. An isograft is a special case: a transplant between identical twins. Because their genetic makeup matches, rejection risk is minimal. A xenograft uses tissue from a different species entirely, such as pig heart valves used in cardiac surgery or bovine bone material used in dental procedures.
Survival Rates After Transplant
Transplant outcomes have improved dramatically over the decades. National one-year survival data from the Scientific Registry of Transplant Recipients shows strong results across all major organs. Kidney transplant recipients have a one-year patient survival rate of about 97%, with the transplanted organ itself surviving in roughly 95% of cases. Liver recipients see about 94% patient survival at one year. Heart transplant recipients have approximately 92% survival at one year.
These numbers reflect averages. Individual outcomes depend heavily on the recipient’s overall health, how well the organ matches, and how consistently they manage their post-transplant medications and follow-up care. Many transplant recipients live decades with their new organs, though some may eventually need a second transplant if chronic rejection or other complications develop over time.
Animal-to-Human Transplants
The persistent shortage of donor organs has driven research into xenotransplantation, particularly using genetically modified pigs. In the most notable recent case, a kidney from a pig with 69 genetic modifications functioned inside a human recipient for 271 days before being removed. Ten of those genetic edits specifically target the biological barriers between pigs and humans: three knock out pig molecules that trigger human immune attacks, and seven insert human genes that help regulate immunity and blood clotting.
The FDA authorized broader clinical trials in 2025, potentially enrolling more than 30 patients across multiple transplant centers for pig-to-human kidney transplants. A parallel trial in China has shown a gene-edited pig kidney functioning for roughly eight months in a patient. These early results are still experimental, but they represent the first sustained proof that heavily engineered animal organs can work in people for extended periods.