immune system disease autoimmune hypersensitivity disease ICD9CM:720 An immune system disease that is an overactive immune response of the body against substances and tissues normally present in the body resulting from an abnormal functioning of the immune system that results in the production of antibodies or T cell directed against the host tissues. disease_ontology hypersensitivity reaction type II disease Xref MGI. ls:IEDB OMIM:109100 DOID:417 autoimmune disease UMLS_CUI:C0003089