Hypersensitivity (also called hypersensitivity reaction or intolerance) is a set of undesirable reactions produced by the normal immune system, including allergiesand autoimmunity. These reactions may be damaging, uncomfortable, or occasionally fatal. Hypersensitivity reactions require a pre-sensitized (immune) state of the host. Comparison of hypersensitivity typesTypeAlternative namesOften mentioned disordersMediatorsDescriptionIAllergy (immediate)AtopyAnaphylaxisAsthmaIgEFast response which occurs in minutes, rather than multiple hours or days. Free antigens cross link the IgE on mast cells and basophils which causes a release of vasoactive biomolecules.Testing can be done via skin test for specific IgE.[2]IICytotoxic, antibody-dependentAutoimmune hemolytic anemiaThrombocytopeniaRheumatic heart diseaseErythroblastosis fetalisGoodpasture's syndromeMembranous nephropathyGraves' disease *see type V explanation belowMyasthenia gravis *see type V explanation belowIgM or IgG(Complement)MACAntibody (IgM or IgG) binds to antigen on a target cell, which is actually a host cell that is perceived by the immune system as foreign, leading to cellular destruction via the MAC.Testing includes both the direct and indirect Coombs test.[3]IIIImmune complex diseaseSerum sicknessArthus reactionRheumatoid arthritisPost streptococcal glomerulonephritisLupus nephritisSystemic lupus erythematosusExtrinsic allergic alveolitis(hypersensitivity pneumonitis)IgG(Complement)NeutrophilsAntibody (IgG) binds to soluble antigen, forming a circulating immune complex. This is often deposited in the vessel walls of the joints and kidney, initiating a local inflammatory reaction.[4]IVDelayed-type hypersensitivity,[2][3] cell-mediated immune memory response, antibody-independentContact dermatitisMantoux testChronic transplant rejectionMultiple sclerosis[5]T-cellsT cells find antigen and activate macrophages.[6]VAutoimmune disease, receptor mediated (see below)Graves' diseaseMyasthenia gravisIgM or IgG(Complement)