TNF and infection: During the acute phase of Schistosoma infection, before parasite oviposition (approximately 5–7 weeks post-infection), immune responses are largely of the CD4+ Th1 type, associated with increased numbers of M1 macrophages that produce IL-12, IL-6, TNF-α and NO (Pearce et al., 1991; Coulson et al., 1998; Gordon, 2003).