This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunity, Subject name: Pathology
Type 1 hypersensitivity reaction differs from type 2 hypersensitivity reaction being? 
Select and explain. 
A. Type 1 reaction is Ig E mediated, B. Type 1 reaction is compliment mediated, C. Type 1 reaction is involves opsonization, D. All of the above
A: Type 1 reaction is Ig E mediated
Answer: A: Type 1 reaction is Ig E mediated 
Explanation: 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.