Threats and Defence Mechanisms

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In this course, different types of threats coming from outside the body, including injury, infections (bacterial, viral, parasitic) and toxins, are analyzed and integrated with the appropriate defence mechanisms. The most relevant entry sites with regard to these threats are the skin, the airways and the gastrointestinal tract. Different threats and different sites of entry (skin, lung, gut) require a diversity of defence mechanisms. 

Hemostasis, inflammation and wound healing are the defence mechanisms against injury and bleeding. Physical, chemical and biological barriers, complement activation, inflammation, and phagocytosis form the first defence mechanisms against invading micro-organisms. Reactive oxygen species are formed by phagocytes to deal with micro-organisms. Also in response to air pollution and nanoparticles, reactive oxygen species are an important defence mechanism. A second line of defence, as well as memory for future threats, is provided by different T- or B-lymphocyte subsets and antibodies. Each of these responses need to be well controlled by homeostatic processes to downregulate the reaction once the threat is conquered. Furthermore, orchestration of all defence mechanisms in order to obtain the most effective response against each type of invading micro-organisms requires optimal communication between immune cells. Consequently, central themes in all defence mechanisms are intra- and intercellular communication and homeostatic responses.