As scientists learned more, it was understood that these proteins and others were part of a broader class of proteins involved in self-defense, and should be called "cytokines".M) concentrations that can increase up to 1,000-fold during trauma or infection.Subsequent cascades of intracellular signalling then alter cell functions.
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.
In this regard, and also because the redundancy and pleomorphism of cytokines are, in fact, a consequence of their homologous receptors, many authorities think that a classification of cytokine receptors would be more clinically and experimentally useful.
A classification of cytokine receptors based on their three-dimensional structure has, therefore, been attempted.
Further, as molecules, cytokines are not limited to their immunomodulatory role.
Cytokines have been classed as lymphokines, interleukins, and chemokines, based on their presumed function, cell of secretion, or target of action.
The effect of a particular cytokine on a given cell depends on the cytokine, its extracellular abundance, the presence and abundance of the complementary receptor on the cell surface, and downstream signals activated by receptor binding; these last two factors can vary by cell type.
Cytokines are characterized by considerable "redundancy", in that many cytokines appear to share similar functions. showed that inflammatory cytokines cause an IL-10-dependent inhibition of Normal tissue integrity is preserved by feedback interactions between diverse cell types mediated by adhesion molecules and secreted cytokines; disruption of normal feedback mechanisms in cancer threatens tissue integrity.
Cytokines also play a role in anti-inflammatory pathways and are a possible therapeutic treatment for pathological pain from inflammation or peripheral nerve injury.
In recent years, the cytokine receptors have come to demand the attention of more investigators than cytokines themselves, partly because of their remarkable characteristics, and partly because a deficiency of cytokine receptors has now been directly linked to certain debilitating immunodeficiency states.
Cytokines are a broad and loose category of small proteins (~5–20 k Da) that are important in cell signalling.