<prompt> Type 1 hypersensitivity reaction differs from type 2 hypersensitivity reaction being?Type 1 reaction is Ig E mediatedType 1 reaction is compliment mediatedType 1 reaction is involves opsonizationAll of the above  <response>: Ans. is a i.e., Type 1 reaction is IgE mediated 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 IgE mediated 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 Immune 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 T cells. 