Immune tolerance the resulting effect is similar. Immune tolerance is important for normal physiology. Central tolerance is the main way the immune system learns to discriminate self from non-self. Peripheral tolerance is key to preventing over-reactivity of the immune 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 immunodysregulation polyendocrinopathy enteropathy X-linked syndrome (IPEX), and potentially contribute to asthma, allergy, and inflammatory bowel disease. And immune tolerance in pregnancy is what allows
Human mortality from H5N1 which is why the disease it causes is called a bird flu. No pandemic strain of H5N1 has yet been found. The precise nature and extent of the genetic alterations that might change one of the currently circulating avian influenza strains into a human flu strain cannot be known in advance. While many of the current H5N1 strains circulating in birds can generate a dangerous cytokine storm in healthy adult humans, the ultimate pandemic strain might arise from a less-lethal strain, or its current level of lethality might be lost in the adaptation to a human host. If H5N1 mutates