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Cytokine

Cytokines are a broad and loose category of small proteins (~5–20 kDa) that are important in cell signaling. Cytokines are peptides, and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrine signaling, paracrine signaling and endocrine signaling as immunomodulating agents. Their definite distinction from hormones is still part of ongoing research. Cytokines include chemokines, interferons, interleukins, lymphokines, and tumour necrosis factors, but generally not hormones or growth factors (despite some overlap in the terminology). Cytokines are produced by a broad range of cells, including immune cells like macrophages, B lymphocytes, T lymphocytes and mast cells, as well as endothelial cells, fibroblasts, and various stromal cells; a given cytokine may be produced by more than one type of cell. They act through receptors, and are especially important in the immune system; cytokines modulate the balance between humoral and cell-based immune responses, and they regulate the maturation, growth, and responsiveness of particular cell populations. Some cytokines enhance or inhibit the action of other cytokines in complex ways. They are different from hormones, which are also important cell signaling molecules, in that hormones circulate in higher concentrations and tend to be made by specific kinds of cells. They are important in health and disease, specifically in host responses to infection, immune responses, inflammation, trauma, sepsis, cancer, and reproduction. The word comes from Greek: cyto, from Greek 'κύτος' kytos 'cavity, cell' + kines, from Greek 'κίνησις' kinēsis 'movement'. Interferon-alpha, an interferon type I, was identified in 1957 as a protein that interfered with viral replication. The activity of interferon-gamma (the sole member of the interferon type II class) was described in 1965; this was the first identified lymphocyte-derived mediator. Macrophage migration inhibitory factor (MIF) was identified simultaneously in 1966 by John David and Barry Bloom. In 1969 Dudley Dumonde proposed the term 'lymphokine' to describe proteins secreted from lymphocytes and later, proteins derived from macrophages and monocytes in culture were called 'monokines'. ln 1974, Stanley Cohen published an article describing the production of MIF in virus-infected allantoic membrane and kidney cells, showing its production is not limited to immune cells. This led to his proposal of the term cytokine.

[ "Genetics", "Internal medicine", "Immunology", "Diabetes mellitus", "Pathology", "Cytokine storm", "Thymic stromal lymphopoietin", "Cytokine Signal Transduction", "bead array", "Janus kinase 1" ]
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