This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
The most important cells in type I hypersensitivity: 
Select and explain. 
A. Macrophages, B. Mast cells, C. Neutrophils, D. Lymphocytes
B: Mast cells
Answer: B: Mast cells 
Explanation: Ans. is 'b' i.e., Mast cells(Ref: Ananthanarayan, 9th/e, p. 162; Robbin's 7th/e, p. 206)* Priming Ag - Antigen presenting cell - T cell - Th 2 - B cell - IgE - Mast cell coated with IgE (Fc).* Shocking dose - IgE (Fab) binds to Ag - Mast cell degranulation.* Primary mediator (Histamine, Serotonin, chemotactic factor) and secondary factor (PG and cytokines) - Typical manifestations like Anaphylaxis etc.