Allograft Inflammatory Factor AIF-1: early immune response in the Mediterranean sea urchin Paracentrotus lividus

Abstract Echinoderms are a phylum of deuterostomic invertebrates that play a key role in maintaining the biodiversity of marine ecosystems. They represent a good study model for immunity because their coelomic fluid contains different types of cells involved in the inflammatory response: the coelomocytes. In the case of the sea urchin Paracentrotus lividus, the coelomocyte population is mainly represented by amoebocytes and uncoloured spherulocytes that implement a defence program through phagocytosis, encapsulation, cytotoxicity, and production of antimicrobial agents. The purpose of this study was to find evidence of a possible modulating effect of lipopolysaccharide LPS on the expression of the AIF-1 gene and therefore to determine whether or not there is a correlation between the P. lividus immune response and the expression of this gene when the homeostasis of the animals is disturbed by a bacterial infection which, in this case, was simulated with treatment with LPS. AIF-1 (Allograft Inflammatory Factor) is a 17 kDa calcium-binding protein that, in vertebrates, is involved in the activation of macrophages. Similarly, in Echinoids and in general in invertebrates, the expression of this gene increases considerably after a bacterial attack and this suggests that it plays a key role during the immune responses.