The word “Cytokines” (cyto-cell; and kinos – movement) is derived from Greek which means “cell movement”. They are intercellular messengers, responsible for signaling an incredible variety of cell functions, such as embryogenesis, hematopoesis, tissue repair, inflammation, immune reactions etc. In terms of origin and purpose they are a more divers’ class of compounds, and are produced by a wide variety of hematopoietic and non-hematopoietic cells.
Cytokines are released by cells directly in to the tissue or in to the circulation and can have autocrine, paracrine and endocrine effects.
They act by binding to their specific receptors located in the cell membrane and initiate a signal cascade in the cell that eventually results biochemical and phenotypical changes in the target cell.
Even though cytokines perform various functions, generically the term cytokines has been used to refer to the immunemodulating agents such as interleukins, interferons, chemokines, growth factors etc. Cytokines play major role in the development and functioning of both the innate and adaptive immune response.
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Cytokines secreted by lymphocytes are referred as lymphokines. Lymphokines are often secreted by lymphocytes that have encountered a pathogen, there by activating and recruiting further immune cells to increase the system’s response to the pathogen.
Autocrine effect, influencing the cell that secreted it.
Paracrine, influencing the cells in the immediate vicinity of a cytokine’s secretions
Endocrine, influencing the cells at distant regions of the body (carried by blood or plasma)