Microbial infection causes the appearance of hemocytes with extreme spreading ability in monolayers of the tobacco hornworm Manduca sexta.
The ability to adhere to and spread on a surface is a common property of insect blood cells. Spreading on a glass surface by insect hemocytes is often used as a measure of immune fitness that can be inhibited by some insect pathogens and parasites. Here, we report that upon infection of the tobacco hornworm Manduca sexta with either a fungus (Beauveria bassiana) or a bacterium (Photorhabdus luminescens), a new type of hemocyte, not previously observed in healthy insects, was found in hemocyte monolayers. These cells have a distinctive morphology, characterised by extreme spreading ability. They achieve a diameter of up to 120 microm after 1 h on glass coverslips and are therefore extremely thin. These hyper-spreading cells first appear in fungal-infected insects prior to hyphal growth. Their numbers later fall to zero as the pathogen begins to proliferate. The same hyper-spreading cells are induced after a 24 h delay following an injection of laminarin, a source of the fungal cell wall polymer beta-1,3-glucans. Wounding, on the other hand, did not cause the appearance of hyper-spreading cells. Evidence is presented here that is consistent with these spreading cells having a role in the cellular immune response of nodule formation.
Dean
Paul
P
Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK. paul.dean@bristol.ac.uk
Richards
Elaine H
EH
Edwards
John P
JP
Reynolds
Stuart E
SE
Charnley
Keith
K
D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects* / Q000276:immunology; D002449:Cell Aggregation / Q000187:drug effects / Q000276:immunology; D048429:Cell Size / Q000187:drug effects* / Q000276:immunology; D005936:Glucans; D006434:Hemocytes / Q000166:cytology* / Q000276:immunology / Q000382:microbiology; D006458:Hemolymph / Q000166:cytology* / Q000276:immunology / Q000382:microbiology; D018402:Manduca / Q000166:cytology* / Q000276:immunology / Q000382:microbiology; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D003904:Mitosporic Fungi / Q000378:metabolism; D020637:Photorhabdus / Q000378:metabolism; D011134:Polysaccharides / Q000494:pharmacology
D005936:Glucans; D011134:Polysaccharides; C008247:laminaran