282 Chapter 11 Appendix 1 - Literature search strategy For this narrative review, a general search was performed with the following terms: (“precision medicine”[MeSH Terms] OR (“precision”[All Fields] AND “medicine”[All Fields]) OR “precision medicine”[All Fields] OR (“personalized”[All Fields] AND “medicine”[All Fields]) OR “personalized medicine”[All Fields]) AND (“sepsis”[MeSH Terms] OR “sepsis”[All Fields]). Key papers were identified by JR, WJW and TvE and provided background information for the introduction and conclusion. References were checked for additional papers. Literature searches for the designated sections were performed by the corresponding authors (see Contributions). Supplementary Electronic Material 1 - Immune status During infection, the innate immune system is in most instances efficient in mounting a protective and balanced response, resulting in elimination of the pathogen. This process is mediated by a variety of pro-inflammatory reactions, such as release of cytokines and chemokines, recruitment and activation of phagocytes to kill pathogens intracellularly and extracellularly [1]. The elimination of the pathogenic microorganism is followed by a return to homeostasis via a set of compensatory mechanisms aimed at tempering the initial inflammation and prevention of collateral tissue damage [2]. While these finelytuned processes are generally very effective for host defence, in certain infections the pathogen succeeds to multiply in spite of the immune response, which then becomes unbalanced and harmful to the host. This dysregulated host response might be caused by specific immune defects that result in an inability to clear the pathogen and activate protective host mechanisms, or due to overwhelming inflammatory reactions triggered by certain virulent pathogens. Sepsis is even more complex since both components, namely a ‘loss-of-function’ and an ‘over-active’ immune response can co-exist. In patients with sepsis, several types of immune imbalances are encountered. Initial concepts proposed more than twenty-five years ago proposed that hyperactivation of the immune system, with exaggerated production of cytokines followed by systemic inflammation, is the main pathologic immune response in sepsis [3, 4]. Subsequently, more recent studies have also shown that immune defects, especially late in the pathologic process, are prevalent and can contribute to mortality [5, 6]. As a consequence, current thinking proposes the departure of immune responses from homeostasis in two opposite directions during sepsis, showing signs of both hyper-inflammation and immune suppression, the extent of which varies between individuals (Figure 2)[7]. Through recognition of pathogen-associated molecular patterns (PAMPs) associated with invading pathogens, and particularly once sepsis is clinically evident, the host response is strongly stimulated to release systemically pro-inflammatory cytokines such as tumour necrosis factor (TNF), interleukin 1 beta (IL-1β) and interleukin 6 (IL6). These and other inflammatory mediators released in the bloodstream will induce generalized inflammation, intravascular coagulation, endothelial activation and fluid extravasation, which can result in hypotension, shock, and organ dysfunction [7]. The response is further derailed due to the release of damage-associated molecular patterns (DAMPs, or alarmins), host-derived molecules released by injured cells which can activate many of the pattern recognition receptors that also recognize PAMPs, giving rise to a vicious cycle with sustained immune activation and organ dysfunction [8].
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