Eine Serie von Aufnahmen zeigt die Reaktion des Immunsystems des Modellinsekts Mehlmotte auf die Infektion mit Fluorescein-5-isothiocyanate (FITC) gefärbten Bakterien.

Hier die detaillierte Beschreibung (veröffentlicht in Altincicek B, Stötzel S, Wygrecka M, Preissner KT, Vilcinskas A. Host-derived extracellular nucleic acids enhance innate immune responses, induce coagulation, and prolong survival upon infection in insects. J Immunol. 2008 Aug 15;181(4):2705-12):

Detection of intrinsic extracellular nucleic acids derived from oenocytoids during insect hemolymph clotting. (A) Microscopic examination of Galleria hemolymph samples containing live hemocytes resulted in the observation that oenocytoids (Oc) rupture within 10-60 s upon bleeding. (B) The rupture of oenocytoids results in visible fibrillar strands that contain nucleic acids since they are positively stained by SYTOX® Green nucleic acid stain (indicated by an arrow). The ‘naked’ nucleus is intensively stained. The granulocyte (Gc) is unstained since the cell is intact. (C, D) Within 1-3 min the granulocytes degranulate substances that entrap FITC-labeled bacteria and results in fibrillar net-like coagulation structures. (E, F) By the hanging drop method (26) we found 3-5 min after bleeding that coagulation strands developed including hemocytes and entrapped FITC-labeled bacteria. (G) Within 5-15 min we observed multi-cell aggregates with enhanced activation of the phenoloxidase cascade resulting in melanisation (brownish color). (H) In these aggregates we detected intense DAPI staining of free cell nuclei of ruptured oenocytoids and faint nuclei staining of intact cells. (I) In order to identify NETs from insect cells we incubated hemolymph samples for 2-5 h in Schneider’s insect medium in the presence of FITC-labeled bacteria and DAPI stain. Hemocytes coagulated with hemolymph proteins and bacteria but no cells were found producing NETs as known from human neutrophils. (J) Overlay of coagulon including DAPI stained nuclei and FITC-labelled bacteria is shown. Aggregated and fragmented nuclei of granulocytes (Gc) and plasmatocytes (Pc) (shown magnified in inserts) indicate apoptotic processes after 3-4 h stimulation whereas ‘naked’ nuclei of oenocytoids (Oc) are highly condensed during incubation period. Note that many bacteria are entrapped by granulocytes and only few are bound to plasmatocytes. Differential interference contrast (Nomarski) and fluorescence imaging; A-D and inserts in J, x 1.575; E-J, x 630. Scale bars: 10 µm.

Kontakt:
Prof. Dr. Andreas Vilcinskas, Dr. Boran Altincicek, Angewandte Entomologie

Mehr zu diesem Thema beim  National Meeting of Developmental and Comparative Immunology am 8. - 10. Oktober 2008 im IFZ