The Body's Defense When Initially Exposed to an Antigen

SCENARIO 1 The body's defense when initially exposed to an antigen SCENARIO The body has a defense system that can recognize antigens or pathogens. The body's initial defense system is always ready and has a non-specific response that can destroy pathogens. These immune components can be in the form of skin, mucosal epithelium, mucous membranes, respiratory tract cilia movement, IgA. 1. Explain the definition, components and mechanisms of the non-specific immune system Guidance Questions for LO 1: a. Is the definition of the immune system non-specific? b. What are the components? c. What is the mechanism? Immunity is defined as resistance to disease, especially infectious disease. The collection of cells, tissues, and molecules that mediate resistance to infection is called the immune system, and the coordinated reaction of these cells and molecules against infectious microbes constitutes the immune response. Immunology is the study of the immune system, including its response to microbial pathogens and damaged tissue and its role in disease. The non-specific immune system can also be called the natural immune system or innate immune system (innate). Definition of non-specific immunity which is also called natural immunity or innate immunity, always present in healthy individuals (hence the name innate), prepared to block the entry of microbes and quickly eliminate microbes that manage to enter the host body. Some principles of non-specific immunity are: • Resistant to infections that every individual has from birth • The immune response occurs within minutes • Previous antigen pre-exposure is not necessary • Limited diversity, activated immunity with limited reactions • Absence of memory immune response • The immune system fights several types of microbes with the same receptors • The antigen receptors in the immune system are not specific for one particular antigen The components of the non-specific immune system are: • Anatomical barriers Anatomical barriers such as skin and mucosa have a spectrum of antimicrobial activity. • Physiological barrier Physiological barriers that contribute to natural immunity are body temperature, pH, and several secretory products in the mucosa. The following are several anatomical, physiological and chemical barriers and their functions in fighting foreign antigens. • Phagocytic cells Phagocytic cells in the form of neutrophils, macrophages, and including monocytes are the main components of the non-specific immune system. There are three stages carried out by phagocyte cells in eradicating antigens. The first stage is that phagocytic cells engulf or phagocyte the antigen to become phagosomes. The second stage is the fusion of lysosomes with phagosomes to form phagolysosomes. The third stage occurs the destruction of foreign antigens. • Natural killer (NK) cells These cells belong to the class of lymphocyte cells that can kill cells infected with viruses or tumor cells. There are cells that belong to the class of lymphocyte cells that are rarely involved, namely--T cells (also called intraepithelial lymphocytes), NK-T cells (found in epithelia and lymphoid organs), B-1 cells (found in the peritoneal cavity and mucosal tissue), and Marginalzone B cells (which are presented at the edges of lymphoid follicles in splenic organ. • Mast cells, macrophages and dendritic cells Mast cells are located in the epithelial lines of the respiratory and other mucosa and are activated via toll-like receptors or IgE antibodies and produce cytoplasmic granules containing histamine, prostaglandins, and cytokines that initiate inflammation and proteolytic enzymes that can destroy bacteria. Dendritic cells act as intermediaries between the natural immune system and the adaptive immune system. • Complement pathway Complement is a humoral immune system of non-specific immunity. Its activation consists of 3 pathways, one of which is the alternative pathway where bacterial endotoxin in the form of mannose stimulates the complement process. The end result of activated complement is lysis of the microbial target, stimulation of inflammation, and stimulation of the adaptive immune system. • Fever and inflammatory response The inflammatory response is a biological response due to stimulus from foreign antigens or microorganisms. Several events resulting from the inflammatory response are vasodilation, plasma leakage, recruitment of phagocytes at the site of infection, phagocytosis of antigens by phagocytic cells, and damage to antigens or microbes. • Normal body flora Normal flora in the intestinal, respiratory and genital mucosa can act as antimicrobials. The way to do this is by competing for nutrients with infectious pathogens or producing antibacterial substances. • Cytokines: TNF--, interleukins (IL-1, IL-6, IL-8, IL-12, IL-16, IL-18), IFN--, -, and TGF Cytokines are produced by dendritic cells, macrophages and other cells which can mediate cellular reactions of natural immunity. Acute phase reactant proteins (APRs) There are several proteins produced by the liver in normal concentrations, and will increase or decrease if there is an acute inflammatory condition. Apart from the liver, there are endothelial cells, fibroblasts, monocytes and adipocytes that can produce this protein. Proteins that increase due to acute inflammatory conditions are Serum amyloid A, C-reactive Protein, Complement protein, coagulation protein, proteinase inhibitors (e.g. antitrypsin), mannose binding protein, haptoglobin, and metal binding protein (e.g. ceruloplasmin). In acute inflammatory conditions, the secretion of APRs that decreases is albumin, transferrin, and antithrombin.The nonspecific immune response mechanism works directly from the initial exposure of the body to a foreign antigen. The body's earliest defense system is the anatomical barrier, which if it is normal and intact, it will be difficult for pathogens to penetrate this barrier and cause infection. Apart from that, pathogens that have virulence factors that can damage the barrier can also invade and cause infection in the body.cause different natural immune reactions. The main natural immune responses to different microbes are: • Extracellular bacteria and fungi are fought primarily through an acute inflammatory response in which monocytes and neutrophils are recruited to the site of infection by the complement system. • Intracellular bacteria that can survive inside phagocytes activate TLRs and other sensors such as cytokines • Defense against viruses is carried out by NK cells and type I interferon. The antiviral mechanism via type I interferon inhibits replication and induces antiviral status, so that healthy or infected cells become resistant to infection. After type I interferon is produced by dendritic cells or infected cells, the signal pathway is activated and inhibits the virus from replicating and destroying the viral genome. The infected virus will be destroyed by NK cells and the ability of NK cells to lyse damaged cells is increased by the presence of type I IFN. •