Allocation is the process of determining how donor organs are distributed. The United Network for Organ Sharing (UNOS) allocates organs based on criteria such as severity of the patient’s condition, blood type, time on the waiting list and others.

Cirrhosis is a disease of the liver in which normal tissue is replaced by scar tissue, which may cause the patient to need a liver transplant.

Cyclosporine is an anti-rejection (immunosuppressive) drug that may be prescribed to prevent organ rejection in people who have received a liver, kidney or heart transplant. It helps slow down your body’s immune system and is usually taken with other medications to help your new organ function normally.

Dialysis is a mechanical process aimed at partially performing kidney functions, such as waste removal and fluid balance. Many kidney patients require frequent dialysis until they receive a transplant.

Donor is a person whose organs or tissues are removed for transplantation. Kidneys and some partial organs may be taken from living donors, but most organs come from a deceased donor.

Immunosuppressive drugs, also called anti-rejection drugs, are medications to prevent your body’s immune system from attacking your transplanted organ. Most transplant patients will need to take immunosuppressive drugs for the rest of their lives.

Procurement is the act of surgically removing an organ from a donor.

Rejection is when the patient’s immune system recognizes the new organ as a foreign body and attacks it. Immunosuppressive drugs are designed to prevent this from happening.

Sensitization happens when a transplant candidate’s blood contains antibodies, which can place him or her at a higher risk of rejecting the new organ. Sensitization can be caused by pregnancy, blood transfusions or rejection of a previous organ transplant.

United Network for Organ Sharing (UNOS) is the private, nonprofit organization that coordinates the national organ transplant waiting list.