Cytokines: Introduction, Properties, and its Functions

this ppt is about the cytokines which is a topic of subject immunology.

1. CYTOKINES:- INTRODUCTION, PROPERTIES, AND FUNCTIONS By:- K hushboo M ishra M.Sc. third semester Department of Microbiology

2. INTRODUCTION The word cytokines are derived from the Greek word, ‘ cyto ’ refers to cells, and ‘ kinos ’ refers to movement. Cytokines are a group of proteins, which includes low molecular glycoproteins or regulatory proteins, which play a significant role in cell-to-cell communication. In response to stimuli, cytokines are secreted by WBC and other cells. It works as a molecular messenger, derived from a variety of cells which includes mast cells, lymphocytes, endothelial cells, macrophage, fibroblast, and granulocyte. The complex interaction between lymphoid cells, hemopoietic cells, and inflammatory cells, is mediated by cytokines. Cytokines are small immunomodulating proteins that range from 5-25 kDa . They are peptide molecules that are important for cell signalling but cannot cross the lipid bilayer of the cell to enter the cytoplasm.

3. PROPERTIES OF THE CYTOKINES An individual cytokine binds to their specific receptor on the same cell membrane, exhibit autocrine action, if it binds to the nearby target cell, then action is called paracrine; in some cases, cytokines may bind to the target cells present in the distant regions of the body, then it is termed as endocrine action. The regulation of the intensity & duration of the immune response is determined by the cytokines, it inhibits or stimulates the activation, proliferation, and differentiation of the different types of the cells and also regulates the production of the antibodies or other cytokines. 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. Different cytokines can stimulate similar functions, meaning they are redundant in nature. They are mostly produced in cascades, as one cytokine estimates the release of other cytokines. Cytokines can work both antagonistically and synergistically. Each cytokine has a matching cell receptor, and it can either upregulate or downregulate the activity of genes.

4. Cytokines may signal cells close to the cell that released them, or they can travel great distances to relay their message. Autocrine signaling: Cytokines can bind to receptors on the same cell that released it. Paracrine signaling: Cytokines can bind to receptors on nearby cells. Endocrine signaling: Cytokines can bind to receptors on cells located far away from the cell that released the cytokines. Cells with cytokine receptors are located throughout your body. In fact, most of your body’s organs contain cells with cytokine receptors. DIFFERENT TYPE OF CYTOKINE SIGNALING/ACTION

5. TYPES OF CYTOKINES Interferons Proteins called interferons prevent viruses from reproducing. Interferons are released when a cell is attacked by a virus. This instructs other cells to raise their defences in order to prevent the virus from spreading. As a result, interferons prevent a virus from spreading. Natural killer T-cells are also activated by interferons . These cells aid in the virus's struggle by eliminating infected cells. Chemokines Chemokines are a type of cytokine that attracts cells to an infection location. Chemotaxis is the ability of a cell to summon other cells by sending a chemical communication. This fact explains why this sort of cytokine is called chemokine: it causes chemotaxis . Chemokines are the battle's coordinators. When a foreign substance is discovered, for example, chemical commands are given to immune cells, which include diverse white blood cells. These cells then proceed to the threat's location in order to eradicate it.

6. Interleukins Proteins called interleukins govern immunological and inflammatory responses. They are mostly produced by white blood cells. Their role is to deliver messages to other white blood cells, informing them that it is time for them to report for duty. Interleukins is a simple name to remember because inter means between cells and leukins means leukocytes. Interleukins allow leukocytes to communicate with one another. Interleukins come in a variety of forms, each with a specific function in the immune system. Immune cells' development, maturation, and activation are among these functions. Tumour Necrosis Factor TNF ( tumour necrosis factor) is a type of cytokine that has the ability to kill cells, including cancer cells. TNF is produced by a variety of cells, although macrophages produce the most. It has the ability to connect to cancer cells and destroy them once released.

7. Types of Cytokines Site of Production Interleukins Produced by TH cells, and mediate communication between leukocytes Lymphokines Produced by Lymphocytes Monokines Produced only by monocytes Interferons Produced by an antiviral response by immune cells Chemokines Produced by immune cells on the response of chemoattractant to mediate chemotaxis TYPES OF CYTOKINES AND THEIR SITE OF PRODUCTION

8. ATTRIBUTES OF THE CYTOKINES Cytokines regulate cellular functions in a coordinated way: Pleiotrophy : An individual cytokine has different effects on distinct target cells, exhibits pleiotropic action. Redundancy: Similar biological activity can be mediated by one or more cytokines

9. Synergy : Combined effect on cellular function by two cytokines Antagonism : One cytokine blocks the effect of the other cytokine

10. FUNCTIONS OF CYTOKINES The variety of cells secretes cytokines, but the major producers are TH cells and macrophages. Cell activation: Cytokines tell cells where to go and what to do. For example, cytokines can direct immune cells toward an infection site so the cells can fight germs there. They can heighten or lessen the processes associated with inflammation. Cell differentiation : Cytokines can tell immature cells to develop into a specific type of cell. For example, cytokines can tell an immature cell to mature into a white blood cell capable of fighting infection. Cell proliferation: Cytokines can tell a cell to make more cells just like it. For example, cytokines can tell a white blood cell to make more white blood cells to fight infection. Cytokines activation is only limited to the antigen-activated lymphocytes, which means cytokines receptors are only expressed when the cell encounters antigen.

11. CONDITIONS AND DISORDER Cytokines are so essential to your immune system that they play a role in most conditions and diseases that may affect you. Typically, cytokines help keep you infection-free. If your immune system releases too many cytokines — in response to an infection or treatments like immunotherapy — you may develop cytokine release syndrome (CRS), also called a cytokine storm. You may develop various symptoms that affect multiple body systems. CRS can be life-threatening without treatment. Too many cytokines can create a heightened inflammatory response. Too much inflammation can damage tissue and lead to diseases and conditions, including: Autoimmune diseases : With autoimmune diseases, your body’s immune cells mistakenly attack healthy cells. Metabolic disorders : Metabolic disorders involve problems with metabolism, the process that allows your body to transform food into energy and remove waste from your body. Cancer. Sepsis: With sepsis, your body’s inflammatory response is so extreme that you experience reduced blood flow to your major organs. Sepsis can be fatal without emergency medical treatment.

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