http://www.ncbi.nlm.nih.gov/disease/Immune.html
Immune_system Asthma Autoimmune polyglandular syndrome Crohn's_disease Digeorge_syndrome Familial_mediterranean_fever Immunodeficiency with Hyper-Igm Severe_combined_immunodeficiency THE IMMUNE_SYSTEM is a complex and highly developed system, yet its mission is simple: to seek and kill invaders . If a person is_born with a severely defective immune_system, death from infection by a virus, bacterium, fungus or parasite will occur. In severe_combined_immunodeficiency, lack of an enzyme means that toxic_waste builds up inside immune_system cells, killing them and thus devastating the immune_system. A lack of immune_system cells is also the basis for Digeorge_syndrome: improper development of the thymus_gland means that T_cell production is_diminished. Most other immune disorders result from either an excessive immune_response or an'autoimmune attack'.'Asthma, Familial_mediterranean_fever and Crohn's_disease (inflammatory_bowel_disease) all result from an over-reaction of the immune_system, while autoimmune polyglandular syndrome and some facets of diabetes are due_to the immune_system attacking'self'cells and molecules. A key part_of the immune_system's role is to differentiate between invaders and the body's own cells-when it fails to make this distinction, a reaction against'self'cells and molecules causes autoimmune_disease