Immunosuppressants are drugs that suppress immune responses. This is necessary, firstly, when transplanting organs and tissues. Currently, doctors can transplant almost any organ (graft) into a person, including the heart. But it is not always possible to force the body to accept a transplanted organ or tissue. This is all due to immune reactions leading to the destruction of the transplant (as the transplanted organ is called) or, as experts say, to its rejection. Another case is autoimmune diseases, when, due to congenital defects, the immune system begins to react to “our own” as if it were “foreign”. The body’s self-destruction begins. In these cases, it is also necessary to resort to immunosuppressants. And finally, allergic reactions caused by an inadequate, overpowering immune response to an antigen.