Not by structures alone: Can the immune system recognize microbial functions?

Inhibitory pattern recognition receptors

“…Microbes with high pathogenic potential can also exist as harmless colonizers of the host, and commensal microbes can cause disease when they behave in an atypical way. Activating PRRs alone cannot differentiate between these situations, and it has thus been suggested that the immune system makes distinctions between pathogenic and nonpathogenic microbes through an integrated system of signals rather than one particular signal ( Greslehner, 2020 ; Swiatczak et al, 2011 ). We argue that iPRRs may provide these additional signals.…”

“…As highlighted by Pradeu and Cooper (2012) , Matzinger later clarified that while the model is theoretical, the idea behind it is that the immune system responds to damage ( Matzinger, 2002 ), and damage signals are much easier to define than danger signals. Since then, many more groups of molecular patterns have been put forward, among which are resolution-, metabolism-, commensal-, and homeostasis-associated molecular patterns (HAMPs; Cario et al, 2002 ; Greslehner, 2020 ; Li et al, 2019 ; Shields et al, 2011 ; Wang et al, 2020 ). Under the term molecular pattern, we now classify groups of molecules that signal the occurrence of a particular event, that elicit similar effects, and that may share common structural features.…”