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nutritional and disease ecology 3

nutritional and disease ecology 3 - Nutritional and Disease...

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Nutritional and Disease Ecology Discuss and evaluate theories linking exposure to infection and the development of allergic disease Scientists across the world are attempting to unravel the complex web of causes in the allergic epidemic. In the last 50 years there has been a dramatic increase in the burden of allergic disease in many developed and industrial countries. This increase has been inversely correlated with a decrease in infectious disease and currently 1 in 5 children in industrialised countries suffer of asthma, allergic rhinitis, and eczema, the so-called ‘allergic diseases’ 1 . Allergies occur when there is an excessive, or hypersensitive, immune response to what would otherwise be a harmless substance. Today asthma is one of the most important allergic diseases and there are approximately 150 million suffers worldwide. There has been a sharp increase in the global prevalence of morbidity, mortality, and economic burden associated with asthma over the last 40 years, particularly in children. 2 There are two types of asthma, extrinsic (non-allergic) and intrinsic (allergic) and this essay will focus on the causes and problems associated with allergic asthma. The Hygiene Hypothesis is one of the most well-known and influential theories that links the exposure to infection to allergies. Later theories have built upon the original hypothesis and scientists are now also investigating the effects that a modern lifestyle has on our susceptibility to allergic diseases. The human immune system provides the ability to respond specifically to foreign proteins (antigens) and to retain a memory of the antigen. There are two main components of the immune system. They may work separately or together. The humoral response involves the production of antibodies by B lymphocytes and the cell-mediated response involves 1 The ISAAC Steering Committee, 1998 Worldwide variation in prevalence of symptoms of asthma, allergic rhinoconjunctivitis and atopic eczema: Lancet ; 351: 1225-32. 2 Braman S. (2006) The Global Burden of asthma, Chest 130: 4s-12S  
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the production of specialised T lymphocytes. 3 The latter response occurs when the body is exposed to bacteria, viruses, fungi, worms and other parasites. Four types of T cells are produced; helper T cells (T h ) which activate B cells, cytotoxic T cells (T c ) suppressor T cells (T s )which regulate the immune response by turning it off when an antigen has gone and the fourth type of T cells (T d ) which protect the body against pathogens, also causing transplant rejection, and inflammation in allergic reactions. 4 Hypersensitivity occurs when the immune system reacts to the wrong substances or over reacts to an antigen. B cells differentiate into anti-body producing cells and the antibodies they produce bind to receptors on the surface of mast cells which contain histamine. When mast cells encounter the allergen again, they bind to it releasing histamine which causes the allergic reactions such as wheezing, inflammation, itching and sneezing. Antibodies are also called immunoglobulins and there are five classes of these molecules. It is the
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nutritional and disease ecology 3 - Nutritional and Disease...

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