All the findings indicate that b integrins play important roles in the balanced activation of immune defense responses as a cell adhesion receptor during infectious encounter in invertebrates. Shrimp is one of the most important commercial aquaculture species in the world, but shrimp aquaculture has been threatened by bacteria and virus diseases and suffered from huge economic losses in the past decades. Monitoring the host immune responses against pathogens would contribute to the development of management strategies for disease control and long-term sustainability of shrimp farming. b-integrin is of fundamental importance in innate immune responses as a cell adhesion receptor during the encounter of infections. Further characterization and more GANT61 500579-04-4 molecular information on b-integrins would be helpful for better understanding the immune system and its regulation mechanisms in invertebrates. Integrins are a large family of cell surface receptors that mediate cell-cell and cell-matrix interactions, and play critical roles in cell migration, differentiation and survival. However, the information and evidences on the involvement of integrins in invertebrate immune defence are still very limited. In the first group, LvIntegrin was clustered with other arthropod b-integrin and then formed an independent invertebrate group with b-integrin from mollusc Crassostrea gigas and Biomphalaria glabrata. In the second group, b-integrin from mammalian firstly clustered together, and then got together with those from poultry, amphibian and fish to form a vertebrate group. Those structural characteristics and phylogenetic relationship indicated that LvIntegrin should be a new member of b-integrin family in shrimps. The spatial structure of b integrin domains in LvIntegrin was established using the SWISS-MODEL prediction algorithm in base of the template 3ijeB, and it was similar to other known b integrin domains. There were two parts in the overall structure of b integrin domains in LvIntegrin, bA and Hybrid domain. The bA domain was consisted of a central six bstrands sheet surrounded by eight helices, and a MIDAS motif occupied a crevice at the top of central strand. The tertiary and quaternary structural rearrangements in integrins can be triggered by its reaction with ligands, which are necessary for cell signaling. The structural rearrangements take place in bA, and bA is a major ligand-binding domain responsible for mediating proteinprotein interactions. In the complex, bA acquires two cations, one of which contacts the ligand Asp directly and the other one stabilizes the ligand-binding surface. The high affinity of cations to the MIDAS of bA mediates the interaction of bA with ligands. The hybrid domain is similar to the I-set Ig domain and it contacts extensively with bA domain to display a mixed hydrophilic and hydrophobic nature. The co-existence of bA and Hybrid domain in LvIntegrin indicates that LvIntegirn may bind to extracellular molecules and generates intracellular signals regulating immune responses in the presence of divalent cations.