Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. In other words, the body really attacks its own cells. This may be restricted to certain organs (e.g. in thyroiditis) or involve a particular tissue in different places (e.g. Goodpasture's disease which may affect the basement membrane in both the lung and the kidney). The treatment of autoimmune diseases is typically with immunosuppression—medication which decreases the immune response.

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