Chapter 16 Tolerance and Autoimmunity Tolerance – a state of unresponsiveness to an antigen

1. Organ-specific autoimmune diseases: Hishimoto ’ s thyroiditis – auto-Abs and sensitized T H 1 cells against thyroid Ags Autoimmune anemias – auto-Abs against RBC Ags or other factors Goodpasture ’ s syndrome – auto-Abs against basement membrane Ags Insulin-dependent diabetes mellitus – auto-Abs against pancreatic  cells Graves ’ disease – auto-Abs against receptors for thyroid- stimulating hormone (TSH) Myasthenia gravis – auto-Abs against acetylcholine receptor

2. Systemic autoimmune diseases Systemic lupus erythematous – attacks many tissues Multiple sclerosis – attacks the central nervous system Rheumatoid arthritis – attacks joints

Proposed Mechanisms for Induction of Autoimmunity 1. Release of sequestered antigens can induce autoimmune disease. 2. Molecular mimicry may contribute to autoimmune disease. 3. Inappropriate expression of class II MHC molecules can sensitize autoreactive T cells.