<unk> , or<unk> logical tolerance, or<unk> tolerance, is a state of unresponsiveness of the<unk>  system to substances or tissue that have the capacity to elicit an<unk>  response in a given organism. It is induced by prior exposure to that specific antigen and contrasts with conventional<unk> -mediated elimination of foreign antigens (see<unk>  response). Tolerance is classified into central tolerance or peripheral tolerance depending on where the state is originally induced—in the thymus and bone marrow (central) or in other tissues and lymph nodes (peripheral). The mechanisms by which these forms of tolerance are established are distinct, but the resulting effect is similar.<unk>  is important for normal physiology. Central tolerance is the main way the<unk>  system learns to discriminate self from non-self. Peripheral tolerance is key to preventing over-reactivity of the<unk>  system to various environmental entities (allergens, gut microbes, etc.). Deficits in central or peripheral tolerance also cause autoimmune disease, resulting in syndromes such as systemic lupus erythematosus, rheumatoid arthritis, type 1 diabetes, autoimmune polyendocrine syndrome type 1 (APS-1), and<unk> dysregulation polyendocrinopathy enteropathy X-linked syndrome (IPEX), and potentially contribute to asthma, allergy, and inflammatory bowel disease. And<unk>  in pregnancy is what allows a mother animal to gestate a genetically distinct offspring with an alloimmune response muted enough to prevent miscarriage. Tolerance, however, also has its negative tradeoffs. It allows for some pathogenic microbes to successfully infect a host and avoid elimination. In addition, inducing peripheral tolerance in the local microenvironment is a common survival strategy for a number of tumors that prevents their elimination by the host<unk>  system.
Immune tolerance
Infectious tolerance
Immune privilege
Peripheral tolerance
Allorecognition
Intravascular immunity
Memory T cell inflation
Immunocompetence