Evolution of innate and adaptive immunity: can we draw a line?

Senescence of the cellular immune response in Drosophila melanogaster

“…In contrast, for invertebrates the mechanisms underpinning immunosenescence are poorly understood, even for the best-characterised invertebrate model, Drosophila melanogaster. Although invertebrates lack the acquired immune responses that are the hallmark of vertebrate immune defence, many innate immunity genes and signalling pathways are functionally conserved between invertebrates and vertebrates [3]. Unravelling the processes which degenerate in the senescence of the D. melanogaster immune system is important to allow exploitation of D. melanogaster as a model for human ageing conditions.…”

Adaptive immunity in invertebrates: A straw house without a mechanistic foundation

“…(30,31) Indeed, it is on the back of this exhaustive and, ultimately, unsuccessful enterprise that comparative immunologists are now confident to assert that invertebrates do not possess vertebrate-like adaptive immunity. (32) The recent papers re-visiting this issue are based more or less entirely on a few individual and unusual host-parasite associations. They cannot therefore offer a general new concept that can be applied across a range of invertebrate taxa.…”

“…Moreover, the descriptor 'immune memory' is not appropriate as it implicitly draws analogy to the vertebrate-acquired response, which is functionally entirely different, relying on clonally derived lymphocyte subsets, RAG genes and MHC I and II, (32) all of which are the key mediators and hallmarks of immune memory in mammals and none of which appear, to date, to exist in invertebrates, urochordates or agnathans. In no sense does the temporary persistence of immune system components within the haemocoel compare with the life-long production of specific immune cells or antibodies, which typify the immune memory of jawed-vertebrates.…”

An evolutionarily and ecologically focused strategy for genome sequencing efforts

“…Although invertebrates do not have the adaptive immune system of vertebrates, the innate components of immunity are strongly conserved across most animals (Flajnik and Du Pasquier, 2004), and many of the functions and features of this branch of immunity have been discovered and best characterized in insects. Most of our mechanistic understanding of invertebrate immunity has been gleaned from a few well-studied species, and is built on work in a single species of fruit fly (Park and Lee, 2011).…”