Neglected biological features in cnidarians self-nonself recognition.

Area of Science:

• * Invertebrate immunology
• * Evolutionary biology
• * Comparative immunology

Background:

• * Cnidarians, simple metazoans, possess innate immunity traits shared across the Animalia kingdom.
• * Histocompatibility is a key cnidarian immune feature, involving allogeneic and xenogeneic responses leading to tissue fusion or rejection.
• * Current research often conflates cnidarian historecognition with host-parasitic interactions or genome-based homology studies with vertebrates.

Purpose of the Study:

• * To critically review overlooked cnidarian immune features: specificity, immunological memory, allogeneic maturation, and natural chimerism.
• * To highlight unique aspects of cnidarian histocompatibility distinct from vertebrate immunology.
• * To advocate for a clearer distinction between historecognition and host-response/disease studies in cnidarians.

Main Methods:

• * Critical review of existing literature on cnidarian immunity.
• * Analysis of 'forgotten' immune features in cnidarians.
• * Comparative analysis with vertebrate immune systems.

Main Results:

• * Cnidarian histocompatibility involves unique cytotoxic outcomes, effector mechanisms, and chimerism not seen in vertebrates.
• * Cnidarians exhibit varied individual responses to immunological challenges, differing from vertebrate adaptive immunity.
• * Features like specificity, memory, allogeneic maturation, and chimerism play critical roles in shaping cnidarian historecognition.

Conclusions:

• * Cnidarian historecognition encompasses unique elements necessitating a re-evaluation of current immunological frameworks.
• * A clearer demarcation is required between immune responses to conspecifics/xenogeneics and host-disease interactions.
• * Further research is needed to synthesize understanding of cnidarian innate immunity and histocompatibility.