Question

Explain two pieces of evidence that exist that some self-reactive lymphocytes in the immune system of a normal, healthy organism can be missed and maintain the potential to raise an autoimmune reaction?  

Answer 1

A basic principle of immunology is that lymphocytes respond to foreign antigens but tolerate self tissues. For developing T cells, the ability to distinguish self from non-self is acquired in the thymus, where the majority of self-reactive cells are eliminated. Recently, however, it has become apparent that some self-reactive T cells avoid being destroyed and instead differentiate into specialized regulatory cells. This appears to be beneficial. Subpopulations of self-reactive T cells have a strong influence on self tolerance and may represent targets for therapeutic intervention to control a variety of autoimmune diseases, tumour growth and infection. In early foetal life, self-reactive lymphocytes that are part of the developing immune system are deleted when exposed to self-antigens. As mentioned above, new immunologically competent cells are generated throughout life and these must be continuously deleted or inactivated also. Lymphocytes are a type of white blood cell that function as part of the immune system. Their various functions allow them to properly respond to foreign invaders in the body. Some lymphocytes work alone, while others are able to coordinate with other cells