G1.5 Alloimmune responses of the gorgonian coral Swiftia exserta

The Scientific and Social Program o f the Vf h ISDCI Congress

G1.5 ALLOIMMUNE

RESPONSES

OF THE GORGONIAN

S1 1 1

CORAL SWIFTIA EXSERTA

Charles H. Bigger, Cecile T. Olano Department of Biological Sciences, Florida International University, Miami, FL 33199, USA Experimental grafting studies have demonstrated that Swifiia exserta, a soft coral, is capable of an adaptive alloimmune response with a memory that can persist for at least eight weeks. To determine the underlying mechanisms, a timed series of allograft rejections was examined with histological and ultrastructural techniques. These were also compared with other studies of normal tissue, autograft fusion and wound healing. The cellular composition and anatomy of S. exserta generally conforms to that reported for other octocorals. Allorejection involves a migration of ceils into the graft zone. Amoebocytes, a heterogeneous cell population are the major constituent. Details of the pathology and mechanisms of tissue destruction will be presented. Unlike hydrozoan allogeneic responses, the tissue damage is not caused by nematocysts (stinging capsules). (Partial support provided by NIH grant RR 08205).

G1.6 ANTIBACTERIAL ACTIVITY IN THE ASCIDIAN, CIONA INTESTINALIS

BLOOD

CELLS

OF

THE

SOLITARY

Valerie J. Smith School of Biological and Medical Sciences, Gatty Marine Laboratory, University of St Andrews, Fife KY 16 8LB, Scotland The blood of the solitary ascidian, Ciona intestinalis, contains a number of distinct blood ceils which act in concert to maintain homeostatic integrity and execute host defence. Previous work with separated cell populations has shown that phagocytosis of bacteria is executed only by the hyaline amoebocytes aided by opsonic factors produced by the morula cells. Little is known about the mechanisms which control the growth of bacteria that may gain access to the circulation. For many animals, bacterial killing by the phagocytes is mediated through the respiratory burst. In C. intestinalis, while the phagocytes produce superoxide ions following stimulation with phorbol myristate acetate, the response tends to be weak and does not result in production of high levels of H202. Viable amoebocytes, enriched on Percoll gradients, do not exhibit marked bactericidal activity against Gram negative bacteria in vitro. However, experiments directed at investigating the nature, location and synergy of antibacterial agents in C. intestinalis has shown that blood cell lysate supernatants have potent antibacterial effects on both Gram negative and Gram positive bacteria in vitro. The response appears to be non-lytic and is not attributable to lysozyme. Comparison of antibacterial vigour by separated blood cell populations indicates that activity resides mainly in the morula ceils, with some activity also present in the amoebocytes.There are certain differences in the response between the two cell types. Antibacterial activity in C. intestinalis therefore seems to rest largely with factors contained within the morula cells and probably occurs during opsonization in vivo.