Rethinking Communication in the Immune System: The Quorum Sensing Concept

Abstract

Quorum sensing was first described as the communication process bacteria employ to coordinate changes in gene expression and therefore, their collective behavior in response to population density. Emerging new evidence suggests that quorum sensing can also contribute to the regulation of immune cell responses. Quorum sensing might be achieved by the ability of immune cells to perceive the density of their own populations or those of other cells in their environment; responses to alterations in cell density might then be coordinated via changes in gene expression and protein signaling. Quorum sensing mechanisms can regulate T and B cell as well as macrophage function. We posit that perturbations in quorum sensing may undermine the balance between diverse immune cell populations, and predisposing a host to immune abnormalities.

Quorum-sensing active particles with discontinuous motility

“…Quorum sensing facilitates the synchronized behavior of bacteria required, e.g., for biofilm formation [8], virulence [9], bioluminescence [10], and motility control [11]. Moreover, there is evidence that quorum sensing also plays a role in the regulation of immune cell responses [12]. Beyond the understanding of large-scale collective behavior of biological entities, such communication mechanisms are interesting for synthetic microrobots with a limited set of responses.…”

Cytotoxic T cells swarm by homotypic chemokine signalling

“…Bottcher, Bonavita, Chakravarty, Blees, Cabeza-Cabrerizo, Sammicheli, Rogers, Sahai, Zelenay, and Reis 2018). Although the concept of bacterial quorum sensing has been applied to coordinated population responses by T cells, the amplification of local T cell densities was shown to occur via differentiation or proliferation (Antonioli et al 2019), relatively long-term effects compared to the rapid directional recruitment of distal CTLs discussed here.…”

Quorum Sensing by Monocyte-Derived Populations

“…Once autoinducer concentration reaches a critical threshold, all bacteria within the autoinducer-rich environment react by modifying their genetic expression and adopt a coordinated behavior (e.g., biofilm formation, virulence factor expression, or swarming motility). Recent advances highlight the possibility that such type of communication is not restricted to bacteria, but can exist among other cell types, including immune cells and more specifically monocyte-derived cells (1). For such cells, quorum sensing mechanisms may not only regulate their population size and synchronize their behavior at homeostasis but also alter their activity and function in unexpected ways during immune reactions.…”