Eicosanoids Mediate Cellar Immune Reactions Of Chrysomya Megacephala Against Mycoplasma Gallisepticum

The immune system of insects have been found to provide defence against a diverse range of exotic, including bacteria, fungi, viruses, protozoans, nematode, parasitoids and insect eggs. Immune response studies of insects related to mollicute are rare. Mollicute size range between viruses and bacteria, no cell wall, exists widely in the soil, slops, insects, vertebrates or humans. Eicosanoids are C20polyunsaturated fatty acids metabolites, metabolized by arachidonic acid (catalyzed by phospholipase A2) on cyclooxygenase and lipoxygenase. Eicosanoids function in many cellular defense functions, including bacteria, fungi, parasitoids and viruses. In this paper, we researched eicosanoids meiate cellar immune reactions of Chrysomya mgacephala against Mycoplasma gllisepticum. The main conclusions are as follows:1. On hemocyte nodulation effectTreating the3rd Chrysomya megacephala larvae was able to recognize with M gallisepticum infections and respond to the invasions by nodulation reactions. The nodulation increased with the concentration of mollicute, and reached a maximum within8h. Dexamethasone (phospholipase A2inhibitor) could reduce the nodulation, and the higher the concentration of the stronger the inhibitory effect. Cyclooxygenase and lipoxygenase inhibitor also inhibited nodulation reactions. The influence of dexamethasone was reversed by the eicosanoid-precursor, arachidonic acid. These findings draw attention to the idea that eicosanoids mediate nodulation reactions to M. gallisepticum challenge in C. megacephala.2. On hemocyte microaggregation effectHemocyte preparations from the3rd larvae of C. megacephala challenged with the M.gallisepticum formed more hemocyte microaggregates than control, and the amount of the hemocyte microaggregates formed in a dose-dependent manner. Furthermore, hemocyte preparations treated with dexamethasone yielded fewer hemocyte microaggregations, and the higher concentration, the less microaggregations. Phospholipase A2and cyclooxygenase inhibitors produced fewer hemocyte microaggregates, but the amount of hemocyte microaggregates was not influenced by lipoxygenase inhibitors. And the influence of dexamethasone was reversed by arachidonic acid. We infer that eicosanoids mediate microaggregation reactions to M. gallisepticum challenge in C.megacephala hemocyte preparations, which mediated mainly by the cyclooxygenase pathway, but not by the lipoxygenase pathway.3. On hemolymph phenoloxidase activity effectPhenoloxidase activity to M.gallisepticum challenge in isolated from the3rd larvae of C.megacephala hemolymph preparations had no significant difference with control. Challenged with the different dose mollicute, the phenoloxidase activity had no significant difference. Phospholipase A2, cyclooxygenase and lipoxygenase inhibitor has no significant effect on phenoloxidase activity. The result showed that, M. gallisepticum challenge can not provoke phenoloxidase activity changes in isolated hemolymph preparations from3rd C. megacephala and eicosanoids have no significant effect on hemolymph phenoloxidase activity.4. On hemocyte migration effectWe used hemocyte preparations from treating the3rd C. megacephala larvae hemolymph with M.gallisepticum,38%hemocytes migrated, higher than the control on24%. Mollicute stimulated hemocytes migrated in a dose dependent manner. Hemocyte preparations treated with dexamethasone inhibited hemocyte migration, and the higher concentration, the low mobility. Hemocyte migration was inhibited by treating the larvae with phospholipase A2, cyclooxygenase and lipoxygenase. The influence of dexamethasone was reversed by injecting arachidonic acid. We infer that M. gallisepticum challenge provokes eicosanoids mediate hemocyte migration reactions in isolated hemocyte preparations from C. megacephala.