Aspects of the Innate Immune System in the Caribbean Octocoral Swiftia exserta

Abstract

All rights reserved.iv ACKNOWLEDGMENTS I wish to thank the members of my committee for their support, patience, and good humor during some very trying times. They selflessly shared reagents, protocols, equipment, and advice; their help has been most appreciated. Using Swiftia exserta, an azooxanthellate ahermatypic local octocoral, as a proxy model organism to study aspects of innate immunity in corals and cnidaria allows us to address both of the reasons listed above while not using endangered species. Utilizing a coral that does not contain symbiotic dinoflagellates (zooxanthellae) simplifies the system by restricting the source of proteins to a single genome. The lack of zooxanthellae in Swiftia exserta also allows the animal's simple adaptation to lab settings.This study of the innate immune system of an octocoral demonstrates: 1) a novel understanding of the microanatomy of octocoral tissues; 2) that Swiftia exserta has at least two cell types that function as constitutive immunocytes; and 3) the presence of two vi potent antibacterial peptides, one with a mass between 4694 and 4696 Daltons. My report on the microanatomy of the coenenchyme, the tissue between polyps, advances the understanding of octocoral anatomy by systematically comparing histology sections with electron micrographs. Applying various techniques of enzyme histochemistry, coupled with cryo-preservation, to the coenenchyme I have identified at least two populations of constitutive immunocytes in Swiftia exserta. Two antibacterial proteins are identified by protein purification and antimicrobial testing techniques. The more active protein is partially characterized with modern hyphenated mass-spectrometry techniques, and can be the focus of future study.

Histology and ultrastructure of the coenenchyme of the octocoral Swiftia exserta, a model organism for innate immunity/graft rejection

“…This is part of a longterm organized study of the cellular/immunological defense responses of S. exserta , a model organism from a phylum that diverged prior to the deuterostome–protostome split, including histological studies of the auto- and allo-graft reactions and phagocytic cells (e.g., Olano, 1993; Bigger and Olano, 1994; Olano and Bigger, 2000; Bigger et al, 2000), on-going studies at the protein and cellular level (e.g., Menzel and Bigger, 2013a, b; Menzel, 2013), and molecular studies to discover an ancient homolog to the complement protein C3 (Dishaw et al, 2005), which plays a pivotal role in activating the immune system. To understand the cellular responses, such as tissue fusion or rejection, response to injury, and foreign body responses, it is truly necessary to first understand the animal’s normal anatomical and cellular condition and structure.…”