The Complex World of Cytokines: Molecular Mediators of Immune Response, Inflammation, and Cell Signaling in Health and Disease.

Cytokines are small proteins that play a crucial role in cell signaling within the immune system. They are secreted by immune cells and influence the behavior of other cells by binding to specific receptors. Cytokines help regulate immune responses, inflammation, and hematopoiesis (blood cell formation). They can be pro-inflammatory, promoting immune responses, or anti-inflammatory, reducing inflammation and promoting healing. Examples include interleukins, interferons, and tumor necrosis factors. Their balance and function are vital for maintaining health and fighting infections or diseases.

1. Cytokines S.Nahidha begum 1 st M.sc . Microbiology Department of Microbiology Sacred Heart college(autonomous),Tirupattur

2. W h at are Cyto k ines ? . Cytokines are small proteins that are produced by immune cells and other cells in the body. They act as messengers, allowing cells to communicate with each other and coordinate the immune response. There are many different types of cytokines, each with its own specific function .

3. Cytokines are small immunomodulating proteins that range from 5-25 kDa. They are involved in paracrine, autocrine and endocrine signalling. Cytokines should not be confused with hormones. Hormones are a more specific kind of molecule as compared to cytokines.  Cytokines are produced by various cells such as macrophages, mast cells, B-lymphocytes, T-lymphocytes , fibroblasts as well as endothelial cells, among others .

4. C yto kine T yp es There are many different types of cytokines, including interleukins , chemokines, and growth factors . Interleukins are involved in communication between immune cells. chemokines are involved in immune cell. migration, and growth factors are involved in cell growth and differentiation .

5. Cytokines Functions Cytokines play a variety of roles in the immune system, including activating immune cells, recruiting immune cells to the site of infection or injury, and modulating the immune response to prevent excessive inflammation . They also play a role in non-immune processes such as cell growth and differentiation .

6. Properties of Cytokines Cytokines may act on the cell that produces them ( autocrine action ), on the nearby cells ( paracrine action ) or on distant cells ( endocrine action ). They are pleiotropic in nature , meaning that a single cytokine can act on different cell types, or different cell types may secrete the same cytokine. They are mostly produced in cascades , as one cytokine estimates the release of other cytokines. Cytokines can work both antagonistically and synergistically

7. CYTOKINES SECRETED BY TARGETS AND EFFECTS SOME CYTOKINES OF INNATE IMMUNITY Interleukin 1 (IL-1) Monocytes, macrophages, endothelial cells, epithelial cells Vasculature (infl ammation); hypothalamus (fever); liver (induction of acute phase proteins) Tumor necrosis factor- α (TNF- α ) Macrophages, monocytes, neutrophils, activated T cells and NK cells Vasculature (infl ammation); liver (induction of acute phase proteins); loss of muscle, body fat (cachexia); induction of death in many cell types; neutrophil activation

8. Interleukin 12 (IL-12) Macrophages, dendritic cells NK cells; infl uences adaptive immunity (promotes TH1 subset) Interleukin 6 (IL-6) Macrophages, endothelial cells, and TH2 cells Liver (induces acute phase proteins); infl uences adaptive immunity (proliferation and antibody secretion of B-cell lineage) Interferon- α (IFN- α ) (this is a family of molecules) Macrophages dendritic cells, virus-infected cells Induces an antiviral state in most nucleated cells; increases MHC Class I expression; activates NK cells

9. Interferon β (IFN- β ) Macrophages, dendritic cells, virus-infected cells Induces an antiviral state in most nucleated cells; increases MHC Class I expression; activates NK cells SOME CYTOKINES OF ADAPTIVE IMMUNITY Interleukin 2 (IL-2) T cells T-cell proliferation;can promote AICD. NK cell activation and proliferation; B-cell proliferation Interleukin 4 (IL-4) TH2 cells, mast cells Promotes TH2 diff erentiation; isotype switch to IgE

10. Interleukin 5 (IL-5) TH2 cells Eosinophil activation and generation Transforming growth factor β (TGF- β ) T cells, macrophages, other cell types Inhibits T-cell proliferation and eff ector functions; inhibits B-cell prolif- eration; promotes isotype switch to IgA; inhibits macrophages Interferon γ (IFN- γ ) TH1 cells, CD8 cells, NK cells Activates macrophages; increases expression MHC Class I and Class II molecules; increases antigen presentation

11. REFERENCE Kuby Immunology (7 TH EDITION) Roitt’s Essential Immunology (10 th EDITION )

12. Thank you