<prompt> Type I hypersensitivity reaction is mediated by:IgGIgMIgDIgE  <response>: In immediate hypersensitivity type I hypersensitivity- the injury is caused by TH2 cells, IgE antibodies, and mast cells and other leukocytes. Mast cells release mediators that act on vessels and smooth muscle and pro-inflammatory cytokines that recruit inflammatory cells. 