Interleukin-6

Interleukin-6 is a pro-inflammatory glycoprotein consisting of 184 amino acids. The gene coding for interleukin-6 is located on the 7th chromosome in humans.

Interleukin-6 binds to specific interleukin-6 receptors (IL-6R = CD126) and forms complexes with them, which bind to the ubiquitous membrane-bound gp-130. The receptors for interleukin-6 are located on T lymphocytes, on activated B lymphocytes, on monocytes, hepatocytes and on B-cell lymphoma cells. 200-1500 receptors are expressed per cell and the gene coding for interleukin-6 is located on the 7th chromosome.

Interleukin-6 is mainly secreted by monocytes/macrophages, but also by epithelial and endothelial cells. Interleukin-6 has broad biological effects.

The cytokine is essentially involved in the regulation of the humoral and cell-mediated immune defence. It promotes the differentiation of CD4+ lymphocytes into Th17 cells. The cytokine also causes the differentiation of B-lymphocytes and macrophages as well as the maturation of megakaryocytes and osteoclasts. The cytokine stimulates the synthesis of the immunoglobulins G and M, the "oxidative burst" in monocytes and neutrophilic granulocytes. Interleukin-6 induces the secretion of acute phase proteins in the liver (C-reactive protein, ferritin, serum amyloid A) as well as the production of other cytokines and acts together with interleukin-1 and TNFalpha as an endogenous pyrogen.

Interleukin-6 stimulates the release of ACTH from the pituitary gland; the resulting glucocorticoids in turn inhibit the production of interleukin-6 (negative feedback between the immune system and the neuroendocrine system).

Standard value: The standard value is up to 10 µg/ml

Still experimental are therapy physicians with monoclonal antibodies that block the IL-6 receptor(tocilizumab) in systemic amlyoidosis.

A smaller study with tocilizumab exists for systemic lupus erythematosus. A significant improvement in the disease activity of SLE was found in 8 out of 15 patients. Arthritis improved in 7 patients, and the concentration of DNA-AK was reduced, as were IgG levels.
There are single case reports of positive effects in systemic scleroderma.

Overexpression of interleukin-6 results in a strong increase in serum IgG1 concentration with possible development of glomerulonephritis. In addition, an increased serum concentration of interleukin-6 appears to be involved in the development of a variety of diseases, e.g. chronic polyarthritis, myeloma, lymphomas, rheumatoid arthritis and liver cirrhosis.

Polymorphisms in the interleukin-6 gene (IL-6-174G/C and IL-6-572G/C) appear to increase the risk of systemic lupus erythematosus.

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