Final answer:
The major histocompatibility complex (MHC) proteins are matched between donor and recipient to decrease organ rejection risks during transplants. MHC matching and immunosuppressive drugs are necessary because the immune system may recognize donated organ MHC molecules as foreign and reject the organ.
Step-by-step explanation:
The major histocompatibility complex (MHC) proteins are one major class of self-antigens. Thus, before an organ transplant, the donor's and the recipient's MHC proteins are matched as closely as possible to decrease the chance of organ rejection.
MHC molecules, particularly MHC class I and class II molecules, are critical as they help the immune system distinguish between self and non-self. They are highly polymorphic, which means there are multiple different MHC genes (alleles) in the human population. During transplantation, if the recipient's immune system recognizes the MHC molecules on the donated organ as foreign, it can initiate an immune response resulting in organ rejection. Therefore, tissue typing to match these MHC proteins as closely as possible between the donor and recipient is essential for successful transplantation.
Aside from matching MHC molecules, transplant recipients are typically given immunosuppressive drugs like cyclosporine A to reduce the immune response and further decrease the chance of rejection. However, even with careful matching and immunosuppression, there is still a risk of rejection due to the complexity of the immune system and the high level of polymorphism in MHC molecules.
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