Furthermore, these infections lead to the increment of various immune-related cells, such as macrophages, mast cells, T-lymphocytes, and pro-inflammatory cytokines (TNF-α, IFN-γ, IL-3, IL-4, IL-5, and IL-6), resulting in low-grade inflammation that has a notable effect on vascular permeability, gastrointestinal motility, secretion, and visceral hypersensitivity, as these play key roles in the development of IBS symptoms [4,66]. The gene discussed is IL4; the disease is infection.