Interleukin-10 indirectly downregulates IL-4-induced production of IgE and directly upregulates IL-4-induced production of IgG4.19 Collectively, these studies have shown that IL10 and TNFα amongst other cytokines play a major role in the pathogenesis and severity of schistosomiasis, and that host immunogenetics is paramount in determining the susceptibility and/or resistance to schistosomiasis. The gene discussed is TNF; the disease is schistosomiasis.