The ‘immunology trap’ of anthozoans

Organisms commonly respond to infectious agents via effector arms of immune systems. However, whereas innate immunity in vertebrates has been intensely investigated, we still strive to understand how cnidarians’ immunity operates, consulting literature that is rife with unsubstantiated statements. Here I contend that the striking superficial similarities with regard to some vertebrate genes promote the false notion that considers vertebrate’s and cnidarian’s immunities as homologous. This is enhanced by intermingling allorecognition with host-parasite interactions and by synthetic comparisons of anthozoans-vertebrates putative immune genes. As complex as it is, cnidarian’s historecognition is probably not associated with host-parasite/disease responses and studies on anthozoan host-parasite interactions are not yet supported by underlying mechanisms. Therefore, I demarcate allorecognition from other aspects of anthozoan immunity and discuss the lack of research studies on the anecdotally recorded anthozoan phagocytes. Further attention is given to the roles of ‘non-immunological defenses’, stand-alone defense mechanisms that respond to environmental assaults independently of immunity, also mistakenly regarded as revealing immune properties. Because defining immunity in the Anthozoa remains deficient, reflecting the needs for improved distinction between historecognition and host-response/disease disciplines, it is required to establish an accepted synthesis for what immunity in cnidarians is or is not, and to evaluate changes in immunocompetence through quantitative approaches. Following the current state-of-the-art on cnidarian immunity, six counsels for re-evaluating immune criteria are offered.