Echinoderm immunity

Abstract

Echinoderms are exclusively marine animals that, after the chordates, represent the second
largest group of deuterostomes. Their diverse species composition and singular ecological niches provide at the same time challenges and rewards when studying the broad range of responses that make up their immune mechanisms. Two types of responses comprise the immune system of echinoderms: a cellular response and a humoral one. Cell-based immunity is carried by the celomocytes, a morphologically heterogeneous population of free roaming cells that are capable of recognizing and neutralizing pathogens. Celomocytes present diverse morphologies and functions, which include phagocytosis, encapsulation, clotting, cytotoxicity, wound healing among others. Humoral immunity is mediated by a wide variety of secreted compounds that can be found in the celomic fluid and play important roles in defense against infection. Compounds such as lectins, agglutinins, perforins, complement and some cytokines make up some of the humoral responses of echinoderms. Recent advances in the field of molecular biology, genomics and transcriptomics have allowed for the discovery of new immune genes and their products. These discoveries have expanded our knowledge of echinoderm immunity and are setting up the stage for future experiments to better understand the evolution of the immune mechanisms of deuterostomes.