Meeting Abstract
In this presentation, we will overview knowledge of metazoan immunity evolution in the context of animal diversity and phylogeny outlined below – discussing trends in methodology and vital gaps in knowledge on conserved and lineage-specific cellular/molecular immune systems. Animals persist in a diverse array of environments laden with pathogenic microbes. To combat infection, metazoans have evolved an array of molecular pathways and cell-types dedicated to recognizing and disposing of pathogenic particles. Coinciding with the evolution of multicellularity in Metazoa, bona fide immunity has been hypothesized to be the result of cooption as a function of the novel requirement for distinguishing between self and non-self (i.e., allorecognition) at the base of the animal tree of life. Even in the earliest diverging animal lineages (i.e., Ctenophora, Porifera, Placozoa, and Cnidaria, respectively), immunity-associated cell types and conventional innate immunity signaling pathway components are identifiable, though with varying degrees of similarity to those in well-described model systems (e.g., Mouse and Human). Within Bilateria, canonical innate immunity pathways are well-recognized and genome analyses indicate several lineage-specific expansions and retractions which have been hypothesized to be a result of invertebrate’s absolute reliance on an immune system which offers no plasticity over an individual’s lifetime. These hypotheses are made in the context of immune systems predating the emergence of vertebrate immunological memory, or “true” adaptive immunities. However, the reliance of comparisons to biomedical model vertebrate systems results in inaccurate assessments of “directional” immunity evolution towards vertebrate-like complexity – perhaps hindering understanding of true immune complexity across Metazoa.
