PCT/IL-6 Combined

PCT is the precursor of calcitonin, which is a glycoprotein composed of 116 amino acids. The molecular amount is about 12.8kd. It has no hormonal activity. Under physiological conditions, PCT is mainly synthesized and secreted by thyroid C cells. During bacterial infection, macrophages and monocytes in the liver, lymphocytes and endocrine cells in the lung and intestinal tissue synthesize and secrete a large amount of PCT under the action of endotoxin, tumor necrosis factor-α and interleukin-6, leading to a significant increase in serum PCT levels.
Interleukin-6 is a cytokine expressed by the innate immune system during initial injury and infection. It is produced by fibroblasts, monocytes/macrophages, T lymphocytes, B lymphocytes, epithelial cells, keratinocytes, and various tumor cells. IL-6 is composed of two glycoprotein chains, one is an α chain with a molecular weight of 80kd; the other is a β chain with a molecular weight of 130kd[5]. If the human body is stimulated by inflammation, IL-6 levels rise rapidly, which in turn mediates the acute phase response of the liver and promotes the production of acute phase proteins such as C-reactive protein (CRP) and serum amyloid A (SAA). Therefore, IL-6 is the earliest marker to rise when inflammation occurs.