What type of transplant, involving genetically identical individuals, typically requires no immunosuppression?

The type of transplant, involving genetically identical individuals, that typically requires no immunosuppression is an isograft. An isograft is a transplant of organs or tissues between two genetically identical individuals, meaning they share the exact same genetic material. A common example of this occurs between identical twins. In such cases, the recipient's immune system, which is the body's natural defense mechanism, recognizes the transplanted tissue as 'self' rather than 'foreign.' This recognition is primarily based on cell surface proteins called major histocompatibility complex (MHC) molecules, also known as human leukocyte antigens (HLA) in humans. Since genetically identical individuals possess identical MHC/HLA molecules, the recipient’s immune system perceives the transplanted tissue as identical to its own cells and does not mount an immune response against it. This absence of an immune attack, or 'rejection,' eliminates the need for immunosuppression. Immunosuppression is the use of medications to suppress or reduce the activity of the immune system, a standard practice in most other types of transplants to prevent the recipient's body from attacking the donor organ.