CYTOKINES (Introduction and Description) by Mohammedfaizan Shaikh
- 2. CONTENET Introduction Properties Nomenclature Classification Immune Cytokines & Their Activity References
- 3. DEFINITION: Secreted, low-molecular-weight proteins that Regulate the nature, intensity and duration of the immune Response by exerting a variety of effects on lymphocytes and/or Other cells. - Cytokines bind to specific receptors on target cells. - Originally were called lymphokines because they were initially - Thought to be produced only by lymphocytes. Then monokines Because they were secreted by monocytes and macrophages. - Then interleukin because they are produced by some Leukocytes and affect other leukocytes. The term “cytokine” is Now used more widely and covers all of the above. - Don’t forget chemokines, they are also considered cytokines.
- 4. • Cytokines are category of signalling molecules that are used extensively in cellular communication. • They are proteins, peptides or glycoproteins. • They are a broad and loose category of small proteins (5-20kda0 that are important in cell signalling. • Cytokine are released by cells and effect behaviour of other of other cells and sometimes releasing cell itself. • They are produced by broad range of cells including immune cells like macrophage, b lymphocytes, t lymphocytes, tumour necrosis factor but generally not hormones or growth factors.
- 5. PROPERTIES Bind to specific receptors on the membrane of target cell. Cytokine receptors may be made up from several different chains. Cytokines & their fully assembled receptors exhibits very high affinity for each other & deliver intercellular signals. Particular cytokine bind to receptors on the membrane I. Autocrine action II. Paracrine action III. Endocrine action Cytokines regulate the intensity & duration of immune response. Exhibit attributes of pleiotropy, redundancy, synergy, antagonism and cascade induction Share many properties with hormones
- 6. - Cytokines act only on cells bearing specific receptors. - Expression of cytokines and their receptors is highly regulated. - E.g. IL-2 receptor
- 7. Cytokines can act in an: - Autocrine (same cell), - Paracrine (close proximity) - Endocrine (long distance)
- 8. 1. Cytokines are pleiotropic … one cytokine can have different effects on different cells.
- 9. 2. Cytokines can be redundant … different cytokines can have the same effects.
- 10. 3. Cytokines can synergize with each other.
- 11. 4. Cytokines can antagonize each other.
- 14. Discovery • Interferon-alpha and interferon type 1 was identified in 1957 as protein that interfered with viral replication. • The activity of interferon gamma was described in 1965;this was first identified lymphocytes derived mediator. • Microphage migration inhibitory factor (mif) was identified simultaneously n 1966 by bloom and benett • IN 1969 DUDLEY PROPOSED TERM lymphokines to describe proteins secreted from lymphocytes and later protein derived from macrophages and monocytes in culture were called monokines • Proteins and other parts of broader class of proteins involved in in self defence, and should be called cytokines.
- 15. NOMENCLATURE • Cytokines are released by cells of immune system by monocytes & t lympho. Also secreted by many cells in addition to those of the immune system such as endothelia cells and fibroblasts. • Interleukin nomenclature was invented to deal with issue of multiple biological properties. • Term IL-1 was used to define a monocyte produced and term IL-2 was used to define lymphocyte product. • But nomenclature did nothing to resolve the border issue of multiple biological properties ascribed to a single molecule. IL-1 was reported cause fever, induce acute phase protein synthesis etc. IL-2 was reported to expand t-cell proliferation and also activate b-cells. Also termed t-cell growth factor and expanded human t-cell in vitro. • LYMPHOKINES, PRODUCED BY LYMPHOCYTES • MONOKINES, PRODUCED BY MONOCYTES • INTERFERONS, INVOLVED IN ANTIVIRAL RESPONSES • CHEMOKINES MEDIATE CHEMO-ATTRACTION (CHEMOTAXIS) BETWEEN CELLS.
- 17. CLASSIFICATION ACCORDING TO FUNCTION • A classification that proves more useful in clinical and experimental practice is dividing cytokines into those that enhance cellular immune responses, type 1 (ifn-γ, tnfα, etc.), And type 2 (tgf-β, IL-4, IL-10, IL-13, etc.), Which favour antibody responses • Some cytokines are primarily lymphocyte growth factors; others function as proinflammatory or anti-inflammatory molecules whereas other cytokines polarize the immune response to antigen. • Il-1, as its properties ranged from effects on control of body temperature to liver protein synthesis to t-cell responses to antigens and mitogens. • Interferon-γ (ifnγ), essential for defence against several intracellular microorganisms such as mycobacterium tuberculosis, is also a major cytokine in the pathogenesis of several autoimmune diseases. • IL-2 is needed for the generation of cytotoxic t-cells (CTL) and forms the basis for several vaccines.
- 18. CLASSIFICATION ACCORDING TO STRUCTURE • Structural homology has been able to partially distinguish between cytokines that do not demonstrate a considerable degree of redundancy so that they can be classified into four types. • Structures of whose members have four bundles of α-helices. This family in turn is divided into three sub-families, the IL-2 subfamily, the interferon (INF) subfamily and the IL-10 subfamily. • The first of these three subfamilies is the largest, and contains several non-immunological cytokines including erythropoietin (epo) and thrombopoietin (thpo). • Il-1 family, which primarily includes il-1 and il-18. IL-17 family, which is yet to be completely characterized.
- 20. REFERENCES Cytokines papers - ahmed g hegazi, department of zoonotic diseases, national research centre, dokki, giza Owen, J. A., Punt, J., & Strandford, S. A. Kuby immunology (6th edition)