<prompt> Atopy in hypersensitivity is -Systemic type I hypersensitivitySystemic type II hypersensitivityLocal type I hypersensitivityLocal type II hypersensitivity  <response>: Type I hypersensitivity occurs in two forms :1. Anaphylaxis2. AtopvAcute, potentially fatal, systemic.Chronic. Nonfatal. Localized.Remember Mast cells are the most important cells in type 1 hypersensitivity.O Eosinophils are the most important cells in the late phase reaction of type I hypersensitivity, Histamine is the most important mediator in type 1 hypersensitivity. 1L-4 is particularly important, it is essential for turning on IgE secreening B cells. PAF is the most important cytokine in the initiation of late phase reaction.Most potent eosinophilic activating cytokine is 1L-5. 