The Th1 and Th2 cell released different kinds of cytokines such as interleukin (IL-2), interferon-gamma (IFN-γ) and tumour necrosis factor-alpha (TNF-α) from TH1 cells and IL-10 produce from Th2 type cells and these cytokines are responsible to stimulates B cell differentiation, production of different immunoglobulin such as IgE, IgG1, IgG4, and IgA, mastocytosis, and eosinophil activation and function (95). The gene discussed is IL2; the disease is mastocytosis.