Cite plausible explanations for the occurrence of auto-immune diseases.?

Question

Cite plausible explanations for the occurrence of auto-immune diseases.?

Answer 1

The thymus is an organ that is responsible for maturation of T lymphocytes.  It is postulated that a dysfunction of the thymus gland improperly allows lymphocytes that recognize self antigens to reach the general circulation and that this is the biochemical basis for auto-immune diseases.  

Answer 2

They occur when the immune system reacts against its own cells by forming autoantibodies, which then destroy its own tissue.

Once the tissue is recognized as foreign, a tissue-specific reaction(IgG & IgM), an immune complex-mediated reaction(antigen-antibodies complexes form), or a cell-mediated reaction occurs(antibodies and sensitized T lymphocytes).