[Inflammation in the blood: what's behind it?]

Inflammation is the body's defensive response to mostly harmful stimuli, usually in response to pathogens or toxic substances. However, the immune response in chronic inflammation is usually directed against harmless antigens, such as allergens, or commensal pathogens, such as herpes viruses, or against the body's own structures, as in autoimmune diseases. The body reacts to the respective stimulating factors with a relatively uniform inflammatory response. Besides the initial reaction of the innate immune system, the activation of immune cells and the release of pro-inflammatory cytokines are in the foreground. Accordingly, inflammatory changes that can be detected in the blood usually do not arise in the blood itself, but in a specific tissue or organ system. In the case of long-term or chronic inflammation, the inflammatory response can be detected in the blood by means of various factors, and both general inflammatory parameters as well as specific parameters can be used for diagnostic purposes. However, the long-term systemic inflammatory response itself also affects the patients suffering from chronic inflammation. This article provides an overview of systemic inflammatory factors relevant for laboratory diagnostics, of how they contribute to specific diseases, and of the systemic effects induced by chronic inflammation.