<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 12-year-old African American is exposed to pollen while playing outside. The allergen stimulates TH2 cells of his immune system to secrete a factor that leads to B-cell class switching to IgE. What factor is secreted by the TH2 cell?? A: IFN-gamma, B: IL-4, C: IL-17, D: TGF-beta, E: IL-22,  <response>: This question is asking about the factor secreted by TH2 cells that leads to IgE production by B cells. The key points are:- 12 year old with pollen allergy - Pollen stimulates TH2 cells- TH2 cells secrete a factor - This factor leads to B cell class switching to IgEIgE is involved in allergic reactions. B cell class switching to IgE production is stimulated by the cytokine IL-4 secreted by TH2 cells.B: IL-4 