The cellular immune responses on insect hosts were studied using an in vitro assay. Hemocytes of different insects hosts with varying level of resistance were exposed to the entomopathogenic nematodes, Heterorhabditis bacteriophora and Steinernema glaseri. The hosts examined were larvae of the wax moth Galleria mellonella, the Japanese beetle, Popilla japonica, the tobacco hawkmoth, Manduca sexta, and the house cricket, Acheta domesticus. For H. bacteriophora, the hemocytes of M. sexta, P. japonica, A. domesticus, and G. mellonella all recognize the nematode in the first hour of encounter to varying degrees corresponding to resistance. In susceptible host G. mellonella, preliminary data shows that recognition is inhibited after 24 hours. For S. glaseri, hemocytes of M. sexta fail to recognize the nematodes. In P. japonica, the S. glaseri could escape from trapping by hemocytes after 24 hours. In A. domesticus, and G. mellonella, resistant and susceptible host for both nematodes respectively, the scenarios of interaction between blood cells and nematodes are the same as those of H. bacteriophora. We hypothesize that the surface coat proteins play an important role in suppressing host immunity. The different immune responses by the hemocytes of M. sexta against H. bacteriophora and S. glaseri suggest that the surface proteins of the two nematode species are different.
Species 1: Rhabditida Heterorhabditidae Heterorhabditis bacteriophora
Species 2: Rhabditida Steinernematidae Steinernema glaseri
Keywords: immune response, entomopathogenic nematode
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