In general, prostaglandins and eicosanoids have potent biological activities in reproduction. For example in the zebrafish egg, high levels of PGE 2 were seen post fertilisation coupled with high PGD 2 synthase transcript levels during the early stages of egg Figure 4 . Images of FhGST-S1 localisation within F. hepatica tissue. A) Anti-F. hepatica FhGST-S1 immunohistochemical stain of a fluke in cross section within the host sheep liver bile duct. Heavily stained eggs (E) are shown released from the fluke into the bile duct in the top left-hand corner. Brown stained areas show the presence of FhGST-S1 proteins. The lack of staining in the host liver (L) highlights the specificity of the antibody. Composite picture. B) Enlarged region of A showing the intense anti-F. hepatica FhGST-S1staining in the voided eggs (E). The spines (S) present in the tegument (T) can be clearly distinguished by their lack of FhGST-S1 presence. C-E) Cross sections of a F. hepatica adult highlighting staining of FhGST-S1 in the parenchyma (P), musculature (M),the tegument (T), basal membrane (Bm) and most intensely in the vitelline cells (V) and developing eggs (DE) . No staining can be seen in the tegumental spines (S), testes (T) or the intestinal caecum (IC). doi:10.1371/journal.pntd.0001666.g004 Figure 5 . rFhGST-SI stimulates the production total prostaglandin and PGE2 from dendritic cells (DCs) in a TLR4 dependent manner. DCs derived from the bone marrow from C57BL/ 6j mice were cultured in vitro with medium, rFhGST-S1 (10 mg/ml) or LPS (100 ng/ml) for 18 hours, and the production of total prostaglandin, PGE2 and PGD2 (data for PGD2 not shown) released into supernatants determined by competitive EIA. Data are presented as the mean 6 SEM following subtraction of medium controls and are representative of two experiments. WT -wild type; TLR4KO -Toll like receptor 4 knock out. doi:10.1371/journal.pntd.0001666.g005