What is Autoimmunity? Why does body reject a transplanted organ?

Explanation

Autommunity is a condition in which structural or functional damage is produced by the action of immunologically competent cells or antibodies against normal components of the body. In other words the immune system of the body goes off the track and starts behaving against the own body or self which leads to a variety of disorders. Autoimmunity literally means "protection against self". It actually implies injury to self and, therefore, the term .Autoallergy. has been suggested as an acceptable alternative. However, the term autoimmunity is widely used.
Two consequences of this ability are to be understood (i) Higher vertebrates can differentiate between foreign molecules and foreign organisms. Most of experiments of immunology are dealt with this aspect, (ii) Sometimes, due to genetic and other unknown reasons, the body attacks self-cells. This causes the damage to the body and is known as auto-immune disease.
Increased helper T cell and decreased suppressor T cell functions have been suggested as causes of autoimmunity.
Examples of autoimmune diseases are rheumatoid arthritis, insulin-dependent diabetes, chronic anaemia, chronic hepatitis, Hashimoto.s disease, etc.
The transplanted organs are sometimes rejected because immune system recognises the non- self ergan. The implanted organ acts as antigenic to the host, which react by the production of T effector lymphocytes. These invade the tissue surrounding the grafted organ and reject the graft. In order to avoid such rejections, the drugs like immunosuppressants (heavy doses of cortisol and cyclosporine) are used.