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The skin is an intricate network of cells engaged in various levels of communication at all times. The most prevalent molecules responsible for this communication are cytokines. Cytokines are proteins, or peptides, that function as biological messengers.
For the skin care practitioner, this article is an introduction the concept of cellular communication, and specifically cytokines. Cell-to-cell communication is emerging as an exciting area in cosmetic product development. Peptides, stem cell technologies, botanicals, vitamins and even less active cosmetic ingredients all have the capacity to positively or negatively affect the skin.
Cytokines are water-soluble chemical compounds that are not stored in the body, but are made as needed for a particular function. There are three individual types of cytokines: autocrine, paracrine and endocrine. An autocrine acts on the cell that produces it. Paracrines act on nearby cells and endocrines act at a long-distance within the body.
Many cells in the body can make cytokines. Lymphokines were the first cytokines to be discovered. They are made by lymphocytes, and are now called interleukins. A great deal of excitement occurred with the discovery that a certain group of cytokines, called interferons, were able to inhibit the growth of viruses. It was found that there were good and bad types of cytokines. Throughout the years, cytokines were classified by their function, rather than their chemical structure. There are many classifications that you will find in medical literature, but these six classes cover most cytokines: growth factors, colony-stimulating factors, cytotoxins, suppressor or inhibitor factors, interleukins and interferon.
Keep in mind that whenever a cytokine is mentioned, it is a messenger that has a specific action on a cell. Many cell types produce and secrete a number of cytokines. In the bloodstream, B and T lymphocyte cells, monocytes and other lymphocytic series secrete a variety of cytokines. In the skin, keratinocytes and Langerhans cells also produce many types of cytokines. Skin care professionals are particularly interested in the cytokines produced by the keratinocytes—and there are quite a few. The keratinocyte can produce all of these interleukins: IL–1, IL-3, IL-6, IL-7, IL-8 and IL-10. In addition, keratinocytes can produce IFN beta and alpha, G-CSF, CSF and G-CSF, along with growth factors including fibroblast growth factor, or bFGF, EGF, KGF, GSA, NGF, TGF-α and -β, as well as PDGF. Let’s look at a few of these cytokines to see what they actually do, in scientific terms. Don’t be discouraged if you don’t grasp it all at once.