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The best studied area for cytokine research is the haematopoietic system. Cytokines are the signalling molecules of cells which act as the agents of immunomodulation. Cytokines are divided based on their immune responses. Mode of action will differ according to the types of cells they are attacking. These are involved in regulating cellular activities. Origin of production of cytokines differentiates its function. Growth factors such as IL-2 are involved in treating cancer. Interleukins are those produced by one type of lymphocytes and affects another type. Signal transduction pathways are involved in stimulation and development of neutrophils, natural killer cells, macrophages and dendritic cells. In this paper, pro-inflammatory and specific or adaptive immunity cytokines and their biological functions are explained in detail. Pro-inflammatory cytokines are the major type involved in immunoregulation and IL-1 is the best example for this.
Cytokines are the single cell secreted protein peptides which includes inflammatory cytokines and growth factors. Those released from inflammatory and connective tissue can alter function of the cell itself and are produced by the macrophages and T helper (Th) cells . Various cells in the body produce various types of cytokines. Three-dimensional structure of the cytokines is not known exactly till date. Its activity can be explained by cell purification and recombination and can be stopped by antagonists . They bind to specific receptors on the target cells to kill them. Among these majorly six types of cytokines are present: Chemokines, interferon's, colony-stimulating factors, transforming growth factor, tumour necrosis factor (TNF) and interleukins . Cytokines are involved in the basophil regulation. New facts about cytokines are still in the process of discovery which will broaden our knowledge about cytokine network. In this paper cytokines and biological functions of the interleukins which are involved in pro-inflammatory and specific immune responses are reviewed.
Cytokines are the chemical messengers that play a major role in regulating the immune responses and mediate cell interactions . These intercellular interactions will effect on growth, survival and also differentiation. These are structurally divided into 4 specific classes. Depending upon their origin of production cytokines has different names: Monokine (from monocytes), lymphokines (from lymphocytes), interleukins (made by one type of leukocytes and acts on the other type of leukocytes). Cytokines possess 3 types of actions: Paracrine action (acts on nearby cells), endocrine action (acts on distant cells), autocrine action (acts on their secretory cells) . In cytokine superfamily I more than 50 types are identified and are mainly produced from macrophages, lymphocytes and leukocytes . Basically cytokine superfamily II are not produced but are formed on cell activation. Mode of action is by interacting with receptors on target cells. Except IL-1 and TNF-Î± most of them gets activated by autocrine or paracrine mechanisms . Factors which influence cytokine action are: Nutrients, toxins, pathogens, hormones, inhibitors and other cytokines. Overproduction of the cytokines may result in the fatal condition called as cytokine storm. Cytokine superfamily III includes functions like formation of another type of cytokines and inducing receptors for them and some of them have antagonistic interaction with others. Signalling language of cytokines is complex and these cytokines are important as pathophysiological mediators . Most of the cytokine signalling includes JAK/STAT signal transduction pathway. Cells of haemopoietic origin are targeted by some growth factors called as INTERLEUKINS. These are non-structural, small, active molecules. They act as mediators of leucocytes and are secreted by mononuclear cells. Currently 35 types of interleukins have been identified . Cytokines responsible for specific immunity includes 4 to 5 types but among those IL-2 is the best one to explain its role. Major function of IL-1 is that it regulates transcription of genes and IL-2 is its involvement in treating diseases. People treated with IL-2 seem to have a major limitation of developing depression
Activated T cells
T cells and mast cells
T cells and mast cells
Activated T cells
thymus and bone marrow stromal cells
Activated T cells
Activated T cells, B cells and monocytes
Macrophages, B cells
Epithelial cells and monocytes
CD8 T cells
Activated memory T cells
Fig.1: Different types of interleukins and major effects of them 
Cytokines that promotes inflammation are called as "pro-inflammatory cytokines".IL-1 and TNF are the best examples for pro-inflammatory cytokines.
IL-1 is a monokine responsible for performing the pro-inflammatory actions and possess different functions in different tissues. It is a hormone like peptide with a molecular weight of 15000. IL-1 family consists of IL-1Î±, IL-1Î² and IL-Ra. In humans these are found in chromosome 2 long arm .IL-1Î± and IL-1Î² are agonistic receptors coded by different genes but show identical biological functions. IL-1Î² production is influenced by the concentration of glucose . Production of interleukin-2 by T-cells is induced by IL-1 . IL-1RI is a specific receptor that mediates the function of IL-1.
Fig.2: Activation of macrophages by IL-1 at specific receptors 
IL-1 activates macrophages and other cells to activate T-cells by binding at specific sites of receptors.
IL-1 causes accumulation of leukocyte, production of prostanoids and cytokines.
Stimulates production of chemokines and synthesis of acute-phase protein.
Cartilage and bone resorption is carried out by IL-1.
Expression of gene is induced by own as that of cyclooxygenase2 and plays a major role in the development of febrile response.
IL-1 activates C/EBF Î² (NF-IL6) and regulates gene transcription of IL-6 and IL-8 .
For many immunological mediated diseases IL-1 acts as pathogenesis mediator.
IL-1ra acts as endogenous neuroprotective molecule in the brain .
Il-1Î² inhibits the secretion of gastric acid.
IL-1ra plays an important role in regulating acute inflammation and also reduces the neuronal damage during the brain injury .
Apoptosis in malignant cells is induced by the interaction of IL-1Î± with RNA processing elements.
IL-1 alpha pertains the stimulation of adrenocorticotropic hormone release in vivo.
Cytokines that are involved in the specific or adaptive immune system are: IL-2, IL-4, IL-5, IL-10 and IFN-y
IL-2 is the first cytokine derived at the molecular level. These are produced in small amounts and are majorly produced by the T-Helper cells in the body . Primary structure is derived from cDNA clones. Body's response towards disease can be improved by IL-2. IL-2 activates T-cells by performing autocrine function. IL-2 becomes toxic when supplied in high doses and it stimulates acquired and innate immune responses.
IL-2 activates extra-cellular signal regulated protein kinase2 (ERK2) [17, 18].
For both T and B-cell lymphocytes IL-2 acts as growth hormone 
It produces cytokines and promotes T-cell production or division.
On proliferating T-cells IL-2 performs autocrine functions.
IL-2 are included in many Immunoregulatory functions like monocyte activation and antibody production (Fig.3)
Parasitic immune responses can be enhanced by IL-2 [2
Vascular function in the diabetic rat can be improved by IL-2 .
IL-2 is used as a therapeutic to treat patients suffering from HIV, renal cancer, Wiskott - Aldrich syndrome (WAS therapy) and melanoma.
IL-2 is important in the survival of antigen-activated T cells and its proliferation .
Natural killer cells can be boosted by small amounts of IL-2 .
IL-2 involves the changes induced by stress and physiological mechanisms in the function of immune system.
Fig.3: Immunoregulatory actions of interleukin-2 
From the past few years research on cytokines is emerging out with new facts and results and is providing knowledge about human normal and abnormal growth of development. Wide range of techniques is present to measure cytokines. Interleukins also plays a major role in the stimulation and production of many chemokines, autocrines and function of immunoregulatory. Pro-inflammatory and specific immune cytokines also function efficiently in stimulating the immune responses. IL-1 activates gene transcription where as IL-2 is used in treating cancer and HIV. But still many experiments are carrying out by various scholars to study the exact mechanisms and the functions involved in treating diseases. Hence further study of cytokines in the field of toxicology may undoubtedly lead to a better understanding about the molecular structure in the coming days.