title: Segmental pairs of giant insect cells discharge presumptive immune proteins at each larval molt.
abstract: A pair of massive secretory cells exists within each thoracic and the nine abdominal segments of Manduca larvae. Each of these cells is nestled between the dorsal integument and underlying muscles. Contents of large vacuoles in these cells are abruptly discharged at each molt and have always been considered to contribute to shedding and/or formation of cuticle. Peanut agglutinin is a specific lectin label for these secretory vacuoles; vacuoles label intensely immediately before each molt as vacuoles attain their maximal size. Contents of vacuoles are restored after each molt and throughout most of each intermolt. During the molt cycle these cells secrete contents of their vacuoles into the interior hemocoel rather than onto the exterior cuticle. Vacuoles discharge via a distinctive mechanism involving partitioning of contents into numerous vesicles that move to the cell surface. Dermal secretory cells were dissected from larvae before and after the 4th-5th instar molt. Proteins from pre-molt and post-molt secretory cells were separated by two-dimensional electrophoresis to establish which proteins are discharged at the molt. While secreted proteins are novel, all have presumptive roles in immune responses. Dermal secretory cells may represent a new, unsuspected component of the innate immune system that release their proteins during the vulnerable molting period of an insect's life.
authors.affiliation: Department of Entomology, University of Illinois, 320 Morrill Hall, 505 S. Goodwin Avenue, Urbana, IL 61801, United States. Electronic address: j-nardi@uiuc.edu.
authors.forename: James B
authors.initials: JB
authors.lastname: Nardi
authors.affiliation: Imaging Technology Group, Beckman Institute for Advanced Science and Technology, University of Illinois, 405 N. Mathews Avenue, Urbana, IL 61801, United States. Electronic address: c-bee1@illinos.edu.
authors.forename: Charles M
authors.initials: CM
authors.lastname: Bee
authors.affiliation: Biological Electron Microscopy, Frederick Seitz Materials Research Laboratory, Room 125, University of Illinois, 104 South Goodwin Avenue, Urbana, IL 61801, United States. Electronic address: lamiller@illinois.edu.
authors.forename: Lou Ann
authors.initials: LA
authors.lastname: Miller
authors.affiliation: Carver Biotechnology Center, 315 Noyes Laboratory of Chemistry, University of Illinois, 505 South Mathews Avenue, Urbana, IL 61801, United States. Electronic address: BSIMAI@illinois.edu.
authors.forename: Brian S
authors.initials: BS
authors.lastname: Imai
authors.affiliation: 315 Noyes Laboratory of Chemistry, University of Illinois, 505 South Mathews Avenue, Urbana, IL 61801, United States. Electronic address: pmyau@illinois.edu.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Yau
mesh_terms: D000818:Animals; D019476:Insect Proteins / Q000378:metabolism*; D007814:Larva / Q000166:cytology; D018402:Manduca / Q000166:cytology / Q000196:embryology* / Q000276:immunology / Q000378:metabolism; D018978:Molting
chemical_list: D019476:Insect Proteins
keywords: Dermal gland; Glycosylated proteins; Innate immunity; Molt; Secretory cell