Antigen-antibody complex mediated hypersensitivity is -

a) Type I reactions (immediate hypersensitivity) → Involve immunoglobulin ‘E’(IgE) mediated release of Histamine and other mediators from mast cells and basophils. b) Type II reactions (Antibody-mediated) → Involve immunoglobulin G or Immunoglobulin M bound to cell surface antigen, with subsequent complement fixation. c) Type III reactions (Immune complex-mediated) → involve circulating antigen-antibody complexes that deposit in postcapillary venules, with subsequent complement fixation. d) Type IV reactions (delayed hypersensitivity cell-mediated) → Mediated by T-cells.