title: The anterior esophageal region of Schistosoma japonicum is a secretory organ.
abstract: BACKGROUND
  The esophagus of blood-feeding schistosomes has been largely neglected although its posterior portion was designated as a gland decades ago. However, we recently showed it plays a pivotal role in blood processing. It is clearly demarcated into anterior and posterior compartments, both surrounded by a mass of cell bodies. Feeding movies revealed that erythrocytes accumulate in the anterior compartment before entering the posterior, indicating that a distinct process is executed there. We therefore investigated ultrastructural aspects and possible functions of the anterior region.
  
  
  METHODS
  The heads of adult Schistosoma japonicum were detached and prepared for both transmission and scanning electron microscopy to define the detailed ultrastructure of the anterior esophagus. Cryosections of heads were also prepared for immunocytochemistry and confocal microscopy to define the pattern of intrinsic host antibody binding in the anterior esophageal lining.
  
  
  RESULTS
  The anterior syncytial lining of the esophagus is highly extended by long, thin corrugations of cytoplasm projecting towards the lumen. Strikingly in the male worm, the tips of the corrugations are further expanded by numerous threads of cytoplasm, producing a spaghetti-like appearance in the central lumen. Flattened, pitted cytoplasmic plates are interspersed in the tangled mass of threads. Abundant, morphologically distinct light vesicles of varied size and contents are manufactured in the cell bodies, from where they traffic through cytoplasmic connections to the corrugations and out to the tips. Clusters of vesicles accumulate in expanded tips in males, together with occasional mitochondria whilst females have more mitochondria but fewer vesicles. The membranous contents of light vesicles are secreted mainly from the tips, but also from the sides of the corrugations. They coat the surfaces and then form organised self-adherent membrane figures when shed into the lumen. Host antibody binds strongly in a characteristic pattern to the anterior esophageal lining indicating that the secretions are highly immunogenic.
  
  
  CONCLUSIONS
  We suggest that the anterior esophageal region is an independent secretory organ. The contents of light vesicles are released into the esophageal lumen via the tips of corrugation to interact with incoming blood. Our immediate task is to establish their composition and role in blood processing.
authors.affiliation: National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, 207 Rui Jin Er Road, Shanghai, 200025, China. xiaohongli1@aliyun.com.|Centre for Immunology and Infection, Department of Biology, University of York, Heslington, York, YO10 5DD, UK. xiaohongli1@aliyun.com.
authors.forename: Xiao Hong
authors.initials: XH
authors.lastname: Li
authors.affiliation: Cytometry Laboratory, Department of Biology, University of York, Heslington, York, YO10 5DD, UK. meg.stark@york.ac.uk.
authors.forename: Meg
authors.initials: M
authors.lastname: Stark
authors.affiliation: Centre for Immunology and Infection, Department of Biology, University of York, Heslington, York, YO10 5DD, UK. gillvance@btinternet.com.
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Vance
authors.affiliation: National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, 207 Rui Jin Er Road, Shanghai, 200025, China. caojp@yahoo.com.
authors.forename: Jian Ping
authors.initials: JP
authors.lastname: Cao
authors.affiliation: Centre for Immunology and Infection, Department of Biology, University of York, Heslington, York, YO10 5DD, UK. alan.wilson@york.ac.uk.
authors.forename: R Alan
authors.initials: RA
authors.lastname: Wilson
mesh_terms: D000818:Animals; D000906:Antibodies; D000909:Antibodies, Helminth; D000918:Antibody Specificity; D004947:Esophagus / Q000502:physiology* / Q000648:ultrastructure; D005260:Female; D034582:Integumentary System / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D012549:Schistosoma japonicum / Q000033:anatomy & histology* / Q000502:physiology*
chemical_list: D000906:Antibodies; D000909:Antibodies, Helminth