This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Atopy in hypersensitivity is - 
Select and explain. 
A. Systemic type I hypersensitivity, B. Systemic type II hypersensitivity, C. Local type I hypersensitivity, D. Local type II hypersensitivity
C: Local type I hypersensitivity
Answer: C: Local type I hypersensitivity 
Explanation: Type I hypersensitivity occurs in two forms :
1. Anaphylaxis
2. Atopv
→
→
Acute, 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.