These harmful substances have proteins called ...

The immune system of your body normally protects you from substances that may be harmful, such as microbes, toxins, and cancer cells. These harmful substances have proteins called antigens on the surface. Once the antigens enter the body, the immune system recognizes them as foreign and attacks them. Similarly, a body which does not comply can cause

or graft rejection. To prevent this reaction, doctors "like" as donor organs and the person receiving the organ. More similar antigens between donor and recipient, the less likely that organ will be rejected. Tissue typing ensures that the organ or tissue is similar to the recipient tissues, but the match is usually not perfect. No two people (except identical twins) have identical tissue antigens. Doctors use different drugs to suppress the immune system and prevent its attack on the newly transplanted organ, when the body does not closely match. If these drugs are not used, the body almost always start the immune response and destroy foreign tissue. There are some exceptions, however. Cornea transplants are rarely rejected because the cornea has no blood supply. Immune cells and antibodies can not reach the cornea causes rejection. In addition, transfer from one twin to another, almost never refused. Hiperostroy rejection occurs within minutes after transplantation, when antigens are absolutely equal. The fabric should be removed immediately, so that the recipient does not die. This type of failure occurs when the recipient receives the wrong blood type. Acute rejection can occur at any time lasix of the first week after transplant 3 months later. Everyone has a number of acute rejection. Chronic rejection occurs over many years. Permanent immune response against the new body slowly destroys transplanted tissue or organ. .