Allergic hy persensitivity is mediated by -

Ans. is 'd' i.e., IgE o Allergic reactions (eczema, hay fever, asthma, atopy) are type I hypersensitivity, which are IgE mediated.Hypersensitivity reactionso The immune system is an integral part of human protection against disease, but the normally protective immune mechanisms can sometimes causes detrimental reactions in the host,o Such reactions are known as hypersensitivity reactions.o Currently the most commonly used classification system of hypersensitivity is that of Gell and coombs classification that divides the hypersensitivity into the following 4 types -1 Type I reactions (immediate hypersensitivity) - Involve immunoglobulin 'E'(Ig E) mediatiate release of Histamine and other mediators from mast cells and basophils.2 Type II reactions (Antibody mediated) -Involve immunoglobulin G or Immunoglobulin M bound to cell surface antigen, with subsequent complement fixation.3 Type III reactions (I mmu ne complex mediated) - involve circulating antigen-antibody complexes that deposit in postcapillary venules, with subsequent complement fixation.4 Type IV reactions (delayed hypersensitity, cell mediated) - Mediated by Tcells.