Basics of Inflammation and Hypersensitivity Reactions

Inflammation is a vascular and cellular reaction to a wide variety of injurious and dangerous stimuli. Many immunological diseases manifest as chronic inflammation. Diseases that are caused by abnormal immune responses and that also involve significant inflammation are called immune-mediated inflammatory diseases. Hypersensitivity describes an abnormal or pathologic immune reaction that is caused by an immune response to repeated exposure to an antigen. Hypersensitivity diseases include autoimmune diseases, in which immune responses are directed against self-antigens, AND diseases that result from uncontrolled or excessive responses to foreign antigens. Because these reactions tend to occur against antigens that cannot be escaped (i.e. self-antigens) and because of positive feedback systems intrinsic to various aspects of the immune response, hypersensitivity diseases tend to manifest as chronic problems. Autoimmunity is the response of the adaptive immune system to self-antigens that occurs when mechanisms of self-tolerance fail.