Amphibian that links mammals and fish is an important taxon in evolution, and Xenopus laevis is a model organism for a long time. With the development of immunology and ecology in 21st Century, amphibian is the model of choice for autarcesiology and ecotoxicology. Due to the exposed skin and the complexity of living conditions, a common thought is that amphibian has a strong innate immune system, such as antibacterial peptides, phagocytes and NK cells. Some species of amphibians are very resistant to lethal pathogen infections, whereas others are more susceptible. And the factors that determine resistance or susceptibility are not well understood. Different compositions of commensal bacteria on the skin and different patterns of inflammation activation (including IL-1β processing) in vivo could explain the contradiction above.The research for these two aspects would contribute to expand our vision in innate immunity. Commensal bacteria were separate from frog skin of Bombina maxima and cultured by Standard I nutrient medium.Then five different bacterial near full-length 16SrRNA sequences were found from cultured bacteria. After sequencing we used RDP- II to identify them, the results showed that these bacteria belonged to five different genera in Proteobacteria, Firmicutes and Actinobacteria. A partial recombinant IL-1β protein was expressed and rabbit polyclonal antibodies against Bombina maxima IL-1β was obtained. Opportunistic pathogen from frog skin was used for intra-abdominal infection and stimulation of splenocytes in vitro. Through the Western blot analysis we found probably inactive pro-IL-1β protein and a putative mature IL-1β. Based on the biochemical analysis and comparation of protein sequence and structure, combined with research progress of non-mammalian IL-1β converting enzyme cut site nowadays, we finally localized the putative Caspase1 cleavage site in Bombina maxima IL-1β.
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