IL4 and parasitic infectious disease: While TH2 cells are described as being producers of IL-4, IL-5, and IL-13, studies using cytokine reporter mice found that T cells, in this case CXCR5+PD1+ T follicular helper cells (TFH), only produce IL-4 in lymph nodes in response to parasite infection, whereas they dominantly produce IL-5 and IL-13 after entering peripheral tissues such as the lungs [5].