Preliminary Study On Cellular Immunity Of Thitarodes Xiaojinensis And Its Immune Interaction With Ophiocordyceps Sinensis

This study aims to identify the types of hemocytes,to determine their percentages in the hemolymph of larvae of the ghost moth,Thitarodes xiaojinensis,and to examine the cellular immune functions of the hemocytes.Further,to explore how Ophiocordyceps sinensis deal with the cellular immunity of T.xiaojinensis larvae.The morphology of hemocytes of 7th instar larvae of T.xiaojinensis was observed under optical phase contrast microscopy and compared with the characteristic morphology of various types of hemocytes of lepidopteran insects..The cellular immune responses of T.xiaojinensis larvae were examined by the stimulation of Saccharomyces cerevisiae and Congo Red stained DEAE-Sephadex A-25.The hemocytes of healthy larvae(HT)and larvae infected with O.sinensis for 7 days(HTO)were observed by scanning electron microscope(SEM)or laser confocal immunofluoreascence microscope through GFP-phalloidin staining.Q-PCR was used to detect the transcriptional level of genes related to F-actins synthesis.The hemocytes of 7th instar larvae of T.xiaojinensis are composed of granular hemocytes,plasmatocytes,spherule cells and oenocytoids,accounting for 62.5%,26.6%,10.1% and 0.8%,respectively.The typical prohemocytes weren't observed.The stimulation of S.cerevisiae causes phagocytosis and nodulation,while the stimulation of Congo Red stained DEAE-Sephadex A-25 causes encapsulation.The results of SEM showed that dense filopodia occurred on the surface of hemocytes of healthy T.xiaojinensis larvae,but the filopodia on the surface of hemocytes of T.xiaojinensis larvae infected with O.sinensis for 7 days were significantly reduced.The microfilament bundles in hemocytes of T.xiaojinensis larvae infected with O.sinensis for 7 days were not obvious and the green fluorescence signal was diffused,showing a clear difference with the identified microfilament bundles in the hemocytes of healthy T.xiaojinensis larvae.The results of Q-PCR test showed that,in the hemocytes of T.xiaojinensis larvae infected by O.sinensis for 7 days,the expression level of DRF was significantly decreased and both Thymosin and Profilin were increased significantly.The composition and morphology of the hemocytes of T.xiaojinensis larvae are the same as those of other lepidopteran insects,and the granular hemocytes have the highest percentage(62.5%).Hemocytes of T.xiaojinensis larvae are sensitive to the stimulation of S.cerevisiae and Congo Red stained DEAE-Sephadex A-25.The former causes phagocytosis and nodulation,and the later causes encapsulation.Therefore,the function of cellular immunity of T.xiaojinensis larvae is typical.O.sinensis reduces the cellular immune capability of T.xiaojinensis larvae through the adverse effects on the formation of filopodia in the hemocytes of T.xiaojinensis larvae.