I am getting a hold on immunological responses at the moment, but I am not familiar yet with the difference between T helper 1 and T helper 2 (Th1, Th2) immune response. I know that: Th1 cells produce IL-2 and IFN-gamma, which activate CD8+ T cells, NK cells, and macrophages; whereas Th2 cells secrete IL-4 and IL-5, which activate B cells and switch antibody synthesis to IgE. So basically a dichotomy in cytokine production, where Th1 seems to be involved in protection against viruses and delayed-type hypersensitivity; Th2 is involved in allergy and parasitic infections. Um, so: Th1 = CD8+ T cells, NK cells, macrophages; Th2 = B cells and IgE. Is there any logic why these two programs are seperated?? There is actually negative feedback between them, if one is activated it will downregulate the other.