Induction of memory-like adaptive responses in murine neutrophils in vitro

Innate immune cells are increasingly recognized for their potential to develop immunological memory. Reports have shown that various cell types (like monocytes, natural killer (NK) cells, as well as microglia) exhibit non-specific memory-like reactions after a secondary insult, a process defined as trained immunity (known also as innate memory). Trained immunity (TRIM) is characterized by increased production of inflammatory mediators (i.e., cytokines, chemokines, reactive oxygen species (ROS)) with associated dynamics in cellular functions (i.e., phagocytosis, migration, anti-microbial and antitumoral activities). Tolerance, the opposing immune reaction, is characterized by a dampened inflammatory state. Both TRIM and tolerance are driven by epigenetic and sub-sequent metabolic changes. Induction of TRIM responses in innate immune cells like neutrophils is challenging due to their short life span. We have established a so called two-hit stimulation protocol in vitro in order to induce memory-like responses in murine bone marrow neutrophils. Here we describe in detail this protocol and how it can be used to enable research in the evolving field of memory-like innate immunity. Pathogen-associated molecular patterns (PAMPs) promote dose-dependent contrasting memory-like responses. Low-dose PAMPs trigger training effects, whereas high-doses result in tolerance responses.

Automated summary

Innate immune cells have the potential to develop immunological memory through a process called trained immunity. This process is characterized by increased production of inflammatory mediators and changes in cellular functions. We have established a two-hit stimulation protocol in vitro to induce memory-like responses in murine bone marrow neutrophils. This protocol can be used to study the evolving field of memory-like innate immunity. Pathogen-associated molecular patterns (PAMPs) promote dose-dependent contrasting memory-like responses.