Blurring Borders: Innate Immunity with Adaptive Features

Abstract

Adaptive immunity has often been considered the penultimate of immune capacities. That system is now being deconstructed to encompass less stringent rules that govern its initiation, actual effector activity, and ambivalent results. Expanding the repertoire of innate immunity found in all invertebrates has greatly facilitated the relaxation of convictions concerning what actually constitutes innate and adaptive immunity. Two animal models, incidentally not on the line of chordate evolution (C. elegans and Drosophila), have contributed enormously to defining homology. The characteristics of specificity and memory and whether the antigen is pathogenic or nonpathogenic reveal considerable information on homology, thus deconstructing the more fundamentalist view. Senescence, cancer, and immunosuppression often associated with mammals that possess both innate and adaptive immunity also exist in invertebrates that only possess innate immunity. Strict definitions become blurred casting skepticism on the utility of creating rigid definitions of what innate and adaptive immunity are without considering overlaps.

Mounting of erratic histoincompatible responses in hermatypic corals: a multi-year interval comparison

“…It is also well documented that invertebrates compensate the absence of adaptive immunity characteristics by using highly variable elements of innate immunity (i.e. FREPs, fibrinogen-related poteins; DsCAM, Down syndrome cell adhesion molecule; SR-Crs, Scavenger receptor cystein-rich domain) (Litman et al, 2005;Kvell et al, 2007).…”

Understanding the vertebrate immune system: insights from the reptilian perspective

“…The protein exhibited strong antibacterial activity against Escherichia coli and Salmonella typhimurium as well as antiviral activity against the Chandipura virus (Chattopadhyay et al, 2006). A -defensin like peptide, pelovaterin, was also found in the eggshell of the Chinese soft- Kvell et al, 2007;24 Turchin and Hsu, 1996. shelled turtle (Lakshminarayanan et al, 2008). Despite low sequence similarity, the protein displayed all of the structural hallmarks of a -defensin.…”

Natural and Pathologic Autoantibodies

“…On the other hand, in vertebrates, adaptive immunity often simply serves as a sophisticated targeting device that recognizes and then processes the antigen but finally leaves the messy job of actually clearing up pathogens to the immense capacity of innate immunity. Therefore, once again we see that borders are blurring and the strict distinction between innate and adaptive immunity might need revision (Kvell et al 2007). Network of natural immunity -including wiled range of different cellular elements and naturally occurring antibodies -could explain as the missing evolutionary chain between the "classic" innate and adaptive immune system.…”

“…Its early evolutionary appearance is indicated by its presence in all multicellular organisms including plants, invertebrates and vertebrates. Since invertebrate species rely on innate defence mechanisms only, survival of the species in the presence of environmental pathogens is achieved at the level of the population, which means that individual members, up until a fraction of total population, are dispensable (Kvell et al, 2007). Innate immunity uses receptors that are ancient in their evolutionary origin.…”

“…One plausible explanation for this is that PRRs were selected and genetically stabilized over an evolutionary time scale creating an advantage for survival, and organisms possessing self reactive PRRs were eventually eliminated. This process prevents autoimmunity in those organisms which have only the innate recognition system (Cooper et al, 2006;Kvell et al, 2007).…”