Th1 CD4+ cells confer immunity to infection by intracellular pathogens through production of effector cytokines IFN-γ, Il-12, TNF, and IL-2, while Th2 CD4+ cells promote the clearance of multicellular helminths and ectoparasites by producing IL-4, IL-5 and IL-10. The gene discussed is IFNG; the disease is infection.