Cytokines despite being nonspecific immunity it regulate the intensity and duration of the inflammatoryimmune response Most cytokines are single polypeptide chains may be aggregate as a homotrimer eg IL12 IL23 ID: 998479
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1. CytokinesCytokines are low molecular weight polypeptide typically function as intercellular messengers mediating their effect via specific receptors on target cells.Cytokines despite being nonspecific immunity it regulate the intensity and duration of the inflammatory/immune response.Most cytokines are single polypeptide chains, may be aggregate as a homotrimer e.g. IL-12, IL-23
2. Important properties of cytokine and chemokineCytokines may act as Autocrine, paracrine, or endocrine.Cytokines may have various attributes: Pleiotropy, Redundancy, Synergize, Antagonize, and cascade. Cytokines encompasses several terms:Interleukins (25), Interferons, Tumor necrosis factors, monokines, lymphokines, and chemokines (50).
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5. Cytokines can be classified based on structure to:Hematopoietin Family: IL-2, IL-4Interferon Family: IFN-betaTumor Necrosis Factor FamilyChemokine familyCytokine can be classified based on the receptors they bind:Growth factors: e.g. CSF-1, SCFIL-1 Family: e.g.IL-1, IL-18TNF Family: e.g. TNF-alpha, CD40L, FASL, LTType I and II cytokinesChemokines
6. ChemokinesChemokines are small polypeptides that selectively control the adhesion chemotaxis and activation of leukocytes. There are four classes of chemokines based on the position of 2 conserved cycteins:1- Alpha-chemokine (CXC): e.g. neutrophil chemoattractants (ELR motif), mononuclear chemoattractans2- Beta- chemokine (CC):mononuclear cell chemoattractant3- gamma-chemokine (C)4- Delta-chemokine (CX3C): neutrophil chemoattractant.
7. Functional classification of chemokines:1- Hemeostatic chemokines: direct hemeostatic distribution of leucocytes to immune tissue e.g. CCL19, CCL21, CXCL12, CXCL 132-Inflammatory chemokines: involve in directing leukocyte traffic during infection and inflammation (chronic and acute) e.g. CCL2, CCL5, CCL11, CXCL8, CXCL9, CXCL10.
8. Cytokine secretion by TH1 and TH2 cells:T helper cells can be divided to Th1 and Th2 subset, Th1 involve in cell-mediated immunity (IL-2, IFN-gamma), Th2 involve in B cell activation and antibody responses (IL-4, IL-5, IL-10)Th1 subset involved in responses to intracellular pathogen (Cytotoxic T cell), Th2 subset involved in extracellular pathogen e.g. promot production of IgM, IgE.Cytokines produced by Th1 and Th2 cell exhibit cross-regulation. IL-10 inhibit IFN-gamma and IL-2.
9. Cytokine ReceptorsCytokine receptors are grouped into 5 mejor families:1- Immunoglobuline superfamily receptors 2- Hematopoietin receptor (class I )3- Interferon receptor family (class II)4- TNF receptor family5- chemokine receptor familyCytokine receptors composed of more than one polypeptide subunit: cytokine-specific polypeptide ; and signal-transduction peptide subuint.IL-2R consisting of 3 subunits(alpha, beta, gamma), alpha is cytokine specific receptor, beta and gamma is signal transduction.Redundancy: have common gamma chain IL-2,IL-4,IL-7,IL-9,and IL-15