1. Cell surface pattern receptors recognize harmful stimuli

2. Inflammatory pathways are activated

Pathogen-associated molecular patterns (PAMPs) trigger inflammatory responses through activation of specific pattern recognition receptors. As a result, the production of proinflammatory cytokines is induced. Proinflammatory cytokines are produced predominantly by activated macrophages and are involved in the upregulation of inflammatory reactions.<ref name="Arti12">Cytokines, inflammation, and pain. International Anesthesiology Clinics, 45(2), 27–37, 2007, Zhang, J.-M., & An, J., https://doi.org/10.1097/AIA.0b013e318034194e </ref> Interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) are cytokines that mediate receptor activation in order to trigger crucial intracellular signaling pathways that may start the healing process.

However, in the case of acute inflammation, the response to an infection is dysregulated and often disproportional to the severity of the infection. The response gets overheated, overactivated, and can damage the body from within. Potential consequences of this overly strong reaction include infections, organ dysfunction (severe sepsis), or septic shock which is a state of circulatory failure where circulatory, cellular and metabolic abnormalities are associated with an increased risk of death. These reactions are often caused by coagulation (i.e. formation of blood clots) dysregulation. The hypercoagulability of sepsis is thought to be driven by the release of tissue factor from disrupted endothelial cells.<ref name="Arti13">Sepsis: The evolution in definition, pathophysiology, and management. SAGE Open Medicine, 7, 2050312119835043–2050312119835043, 2019, Gyawali, B., Ramakrishna, K., & Dhamoon, A. S., https://doi.org/10.1177/2050312119835043 </ref> When the human body suffers from severe sepsis, activated monocytes and endothelial cells, along with circulating microvesicles, become sources of tissue factor<ref name="Arti14">Role of extracellular vesicles in the development of sepsis-induced coagulopathy. Journal of Intensive Care, 6, 68, 2018, Iba, T., & Ogura, H., https://doi.org/10.1186/s40560-018-0340-6 </ref>.

This factor then causes the systemic activation of the coagulation cascade resulting in the production of thrombin, activation of platelets, and formation of platelet–fibrin clots. These structures can result in local perfusion defects leading to tissue hypoxia and organ dysfunction <ref name="Arti13">Sepsis: The evolution in definition, pathophysiology, and management. SAGE Open Medicine, 7, 2050312119835043–2050312119835043, 2019, Gyawali, B., Ramakrishna, K., & Dhamoon, A. S., https://doi.org/10.1177/2050312119835043 </ref>. Moreover, research has shown that dysregulated apoptotic immune cell-death plays a crucial part in immune dysfunction and mortality of sepsis. Apoptosis is a “programmed cell death” to limit damage of surrounding tissue during the immune response<ref name="Arti15">Apoptosis: a review of programmed cell death. Toxicologic Pathology, 35(4), 495–516, 2007, Elmore, S., https://doi.org/10.1080/01926230701320337 </ref>. It is a vital component of many processes in the human body such as cell turnover, proper development and functioning of the immune system ref name="Arti15">Apoptosis: a review of programmed cell death.<ref name="Arti15">Apoptosis: a review of programmed cell death. Toxicologic Pathology, 35(4), 495–516, 2007, Elmore, S., https://doi.org/10.1080/01926230701320337 </ref> Most cells that undergo enhanced apoptosis in sepsis are of lymphoid origin, hence less immune cells are left to fight off the infection itself <ref name="Arti16">Host–pathogen interactions in sepsis. The Lancet Infectious Diseases, 8(1), 32–43, 2008, van der Poll, T., & Opal, S. M., https://doi.org/https://doi.org/10.1016/S1473-3099(07)70265-7 </ref>. Since no effective treatment for sepsis exists yet, early diagnosis and recognition is crucial.<ref name="Arti17">Sepsis and septic shock: current approaches to management. Internal Medicine Journal, 49(2), 160–170., 2019, Thompson, K., Venkatesh, B., & Finfer, S., https://doi.org/10.1111/imj.14199 </ref>