Innate immune memory: An evolutionary perspective

Abstract

Over the last decades, there was increasing evidence for the presence of innate immune memory in living organisms. In this review, we compare the innate immune memory of various organisms with a focus on phylogenetics. We discuss the acquisition and molecular basis of immune memory and we describe the innate immune memory paradigm and its role in host defense during evolution. The molecular characterization of innate immunological memory in diverse organisms and host-parasite systems reconciles mechanisms with phenomena and paves the way to molecular comprehension of innate immune memory. We also revise the traditional classification of innate and adaptive immunity in jawed vertebrates. We emphasize that innate immune responses have the capacity to be "primed" or "trained", thereby exerting a yet unknown type of immunological memory upon re-infection.

Coronavirus activates a stem cell-mediated defense mechanism that reactivates dormant tuberculosis: implications in COVID-19 pandemic

“…MHV-1 infection model and immune response, the role of trained immunity has not been evaluated. The trained immunity constitutes innate immune memory where hematopoietic cells may undergo cell intrinsic changes including metabolic and epigenetic modifications to remember pathogenic insult (45)(46)(47)(48)(49)(50). Trained immunity of MSCs has not yet been studied.…”

Defining trained immunity and its role in health and disease

“…However, a growing body of literature indicating that innate immune cells -and even tissue-resident stem cells -can show adaptive characteristics has challenged this dogma [4][5][6][7][8] . Greater protection against reinfection -a de facto immune memory function -has also been reported in plants and invertebrates [9][10][11] , which lack an adaptive immune system. This demonstrates that adaptation of host defence can occur on the basis of innate-like immune mechanisms.…”

“…Given the evolutionary success of organisms lacking adaptive immune responses, which represent up to 97% of the total biodiversity on Earth 20 , it is unlikely that immunological memory has evolved only in vertebrates. Indeed, over the past two decades, an increasing number of studies have provided evidence that the immune system of plants and invertebrates may be 'primed' by an initial infection, leading to protection against subsequent infections 10,11,18,19,21,22 . Likewise, memory characteristics in the innate immune system of vertebrates have recently been described and referred to as 'trained immunity' , a process that results in a heightened reaction to secondary infections or sterile triggers of inflammation 5,12 .…”

Innate and Adaptive Immune Memory: an Evolutionary Continuum in the Host’s Response to Pathogens

“…That immune memory is advantageous from an evolutionary point of view is well illustrated by deadly ancient diseases such as smallpox: while mortality was historically 20%-60% for first infections, individuals became completely immune to the disease thereafter (Riedel, 2005). Therefore, it is difficult to envision that immune memory evolved only in vertebrates, which represent approximately 1%-2% of living species (Gourbal et al, 2018). In contrast, other important advantageous traits, such as vision, evolved independently several times during the evolution of various groups of animals (so called ''convergent evolution'') (Gehring, 2004).…”