The acute phase response is a physiological response to disturbances in homeostasis, such as infection, tissue injury, or immunological disorders. This response involves a local reaction at the site of injury and a systemic reaction characterized by fever, leukocytosis, increased erythrocyte sedimentation rate, and changes in hormone levels. Acute phase proteins, which are synthesized primarily in the liver, play a crucial role in this response. Interleukin-6 (IL-6) is a key cytokine that regulates the synthesis of these proteins. IL-6 is produced by various cells, including monocytes, macrophages, fibroblasts, and endothelial cells, and acts on hepatocytes to induce the synthesis of acute phase proteins. The interaction between IL-6 and its receptor on hepatocytes is essential for the regulation of acute phase protein synthesis. IL-6 also has pleiotropic effects, influencing immune and hematopoietic systems, and is involved in the expression of class I histocompatibility antigens. Understanding the mechanisms of the acute phase response, including the regulation of IL-6 production and its signaling pathways, is crucial for improving the treatment of inflammatory diseases.The acute phase response is a physiological response to disturbances in homeostasis, such as infection, tissue injury, or immunological disorders. This response involves a local reaction at the site of injury and a systemic reaction characterized by fever, leukocytosis, increased erythrocyte sedimentation rate, and changes in hormone levels. Acute phase proteins, which are synthesized primarily in the liver, play a crucial role in this response. Interleukin-6 (IL-6) is a key cytokine that regulates the synthesis of these proteins. IL-6 is produced by various cells, including monocytes, macrophages, fibroblasts, and endothelial cells, and acts on hepatocytes to induce the synthesis of acute phase proteins. The interaction between IL-6 and its receptor on hepatocytes is essential for the regulation of acute phase protein synthesis. IL-6 also has pleiotropic effects, influencing immune and hematopoietic systems, and is involved in the expression of class I histocompatibility antigens. Understanding the mechanisms of the acute phase response, including the regulation of IL-6 production and its signaling pathways, is crucial for improving the treatment of inflammatory diseases.