Coral immunology and resistance to disease

Abstract

Scleractinian corals (phylum Cnidaria, class Anthozoa) have innate immunological responses against infections. Research has recently suggested that corals also possess an adaptivelike immunological repertoire that recognizes specific pathogens and allografts. While evolutionarily distinct, the corals' innate and adaptive-like immunity systems are not mutually exclusive because the phagocytic cells of the non-specific, innate immune system may activate specific adaptive immunological responses. Warming oceans may immunocompromise coral hosts, making them more susceptible to tropical marine diseases, independent of the virulence of the pathogen. The ability of corals to ward off both primary and opportunistic infections, through adaptive-like mechanisms, may play a critical role in the corals' ability to fight future disease infection. Here we show evidence that corals possess immunological repertoires that extend well beyond simple innate defenses. The extent to which corals have developed such an adaptive-like immune repertoire will determine whether corals will survive climate change and other anthropogenic disturbances.KEY WORDS: Coral · Anthozoan genome · Coral immunology · Holobiont · Coral amoebocytes · Symbionts · Compromised-host hypothesis · Acropora millepora Resale or republication not permitted without written consent of the publisherDis Aquat Org 90: [85][86][87][88][89][90][91][92] 2010 brates contain only innate-immune defenses. The Hildemann group found that isografts (using the same colony) of the Hawaiian stony coral Montipora verrucosa were consistently compatible and fused within days of grafting, whereas allografts (from different colonies) resulted in soft-tissue death. Furthermore, the reaction time was accelerated by almost 50% when the same allograft pairs were reset. The authors summarized their results as showing 'both specificity in transplantation alloimmunity and extensive antigenic polymorphism among genetically separate M. verrucosa. ' (Hildemann et al. 1977). Moreover, researchers discovered that Vibrio shiloi, the bacteria that previously infected the stony coral Oculina patagonica in the eastern Mediterranean, is now lysed upon entering the coral tissue . How is such an expanded immunological repertoire possible for scleractinian corals?Metazoan invertebrates have evolved polymorphic histocompatibility mechanisms without the use of antibodies. For example, the innate-immune response of a freshwater hydrozoan polyp was found to be mediated by unconventional toll-like receptor (TLR) signaling (Bosch et al. 2009). Additionally, genetic studies of a marine hydrozoan, Hydractinia symbiolongicarpus, revealed an invertebrate histocompatibility complex. Tools are now at hand to isolate homologs of higher chordate immune system molecules and identify invertebrate allorecognition determinants (Mokady & Buss 1996, Cadavid et al. 2004, Dishaw & Litman 2009). This type of genetic approach has not yet been fully applied to reef corals.Conventional wisdom suggests that scleractini...

Patterns of coral ecological immunology: variation in the responses of Caribbean corals to elevated temperature and a pathogen elicitor

“…Recent studies into coral immunity demonstrate that corals possess many innate immune mechanisms similar to those of other invertebrates (for reviews, see Dunn, 2009;Mydlarz et al, 2010;Reed et al, 2010). Prophenoloxidase (PPO) is the activating enzyme of the melanin-synthesis pathway, which is a key component of invertebrate immunity (Cerenius et al, 2008).…”

Systematic Analysis of White Pox Disease in Acropora palmata of the Florida Keys and Role of Serratia marcescens

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