During the shift from terrestrial to aquatic environment and the diversification into various aquatic environment, dolphins were probably confronted with numerous challenges caused by stressors from the changing environments. Furthermore, dolphins are the main sentinel species because their biological characteristic. Dolphins can expose current or potential negative impacts on individual- and population-level animal health and better characterization and management of impacts that ultimately affect animal and human health associated with the oceans. Therefore, dolphins play the crucial role in marine environment and ecosystem.

The increasing environmental pressure urges cetaceans to own the dynamic immune system that could help them adapted the complex aquatic environment. The immune system plays a crucial role in the survival and reproduction of dolphins in a severe environment. Toll-like receptors (TLRs) as the typical pattern-recognition receptors (PRR) play a crucial role in both innate immune system and adapted immune system.

Our experiment subject is Pantropical Spotted Dolphin fibroblast (PSDF) cell line. Because studies of TLRs in dolphin fibroblast are not clear, we have to confirm the expression of TLRs family in PSDF cell line. After aligning TLR4 sequences among dolphin and other terrestrial mammals, we found dolphin TLR4 is most dissimilar to mouse TLR4 which is the typical laboratory animal. We predicted that dolphins TLR4 caused immune response may vary from laboratory animals.

Interleckin-6(IL-6), interleckin-8(IL-8), interleukin-1β (IL-1β), tumor necrosis factor alpha (TNF-α) as well as TLR4 mRNA expression were measured at four time (0, 6, 12 and 24 hours) after stimulation of E.coli LPS (1000ng/ml) in PSDF and mouse fibroblast (L929). IL-6 is distinctly up-regulate in L929 after treated 24 hours. But in PSDF the top expression of IL-6 is 6 hours group. The expression of IL-8 in L929 is lower than in PSDF. All cytokine results show dolphin can release pro-inflammatory factors quicker than mouse. Autodock vina shows the dock locations of LPS and TLR4 and docking sites are different between dolphin and mouse which might explain probably reason of the immune response differences.