Macrophages and the maintenance of homeostasis

Abstract

There have been many chapters written about macrophage polarization. These chapters generally focus on the role of macrophages in orchestrating immune responses by highlighting the T-cell-derived cytokines that shape these polarizing responses. This bias toward immunity is understandable, given the importance of macrophages to host defense. However, macrophages are ubiquitous and are involved in many different cellular processes, and describing them as immune cells is undoubtedly an oversimplification. It disregards their important roles in development, tissue remodeling, wound healing, angiogenesis, and metabolism, to name just a few processes. In this chapter, we propose that macrophages function as transducers in the body. According to Wikipedia, “A transducer is a device that converts energy from one form to another.” The word transducer is a term used to describe both the “sensor,” which can interpret a wide range of energy forms, and the “actuator,” which can switch voltages or currents to affect the environment. Macrophages are able to sense a seemingly endless variety of inputs from their environment and transduce these inputs into a variety of different response outcomes. Thus, rather than functioning as immune cells, they should be considered more broadly as cellular transducers that interpret microenvironmental changes and actuate vital tissue responses. In this chapter, we will describe some of the sensory stimuli that macrophages perceive and the responses they make to these stimuli to achieve their prime directive, which is the maintenance of homeostasis.

The immune‐enhancing effect of anthocyanin‐fucoidan nanocomplex in RAW264.7 macrophages and cyclophosphamide‐induced immunosuppressed mice

“…The prime function of macrophages to sense their environment is to achieve homeostasis via regulating the process of inflammation and effectively defending against pathogens (Mosser et al, 2020;Wynn et al, 2013). Macrophages are an incredibly various subsets such as classically activated macrophages or alternatively activated macrophages that constantly transduce their functional state into new set points in response to changes in their surroundings (Wynn et al, 2013).…”

Mechanisms of Macrophage Plasticity in the Tumor Environment: Manipulating Activation State to Improve Outcomes

“…Taken together, these studies call the M1/M2 polarization paradigm into question. While, to some extent, supporting the notion that a spectrum of intra-tumoral macrophage activation states exist (275,276), the finding of simultaneous M1 and M2 associated markers by macrophages is quite novel. Perhaps historical use of conventional models coupled with aggregate analyses of pooled macrophage populations fail to detect a more widespread phenomenon of M1/M2 marker co-expression in tumors.…”

Murine myeloid cell MCPIP1 suppresses autoimmunity by regulating B-cell expansion and differentiation

“…Furthermore, phagocytes regulate the kinetics of necrotic cell clearance to restrict the concentration of potential auto-antigens within the tissue ( Fond and Ravichandran, 2016 ; Mistry and Kaplan, 2017 ). Finally, yet importantly, they are key regulators of inflammation ( Mosser et al, 2021) . These necessary checkpoints within innate immune responses limit the production of autoantibodies and immune complex deposition that trigger autoimmune organ damage.…”