Microbiology and Parasitology - Immunology 1 PDF

MICROBIOLOGY AND PARASITOLOGY 08/28/2024. MOD 4: IMMUNOLOGY 1 Ludivina Tesoro-Solis,...

MICROBIOLOGY AND PARASITOLOGY 08/28/2024. MOD 4: IMMUNOLOGY 1 Ludivina Tesoro-Solis, MD, FPSP Trans Group/s: 7B, 8B I. INTRODUCTION FUNCTION OF THE IMMUNE SYSTEM We're all constantly exposed to microorganisms and their metabolic products that can cause disease. 1 Surveillance of the body There are times that you get well from your sickness whether or not you take your medications. 2 Recognition of foreign material such as pathogen Immunology deals with how our body handles infection. ○ How it deals with what is perceived as non self. 3 Attack and destruction of foreign invaders A. FUNCTION OF IMMUNE SYSTEM B. TYPES OF IMMUNITY (INNATE VS. ADAPTIVE) In our body, there are cells and tissues that work to defend itself against infections and this is collectively INNATE IMMUNITY ADAPTIVE IMMUNITY known as the immune system. (Non-specific Immunity) (Specific Immunity) It helps the body fight infection through a complex, coordinated interplay of cells and tissues in the body Resistance is pre-existing Acquired after antigen through an immune response. (present at birth) exposure Surveillance of the body → recognition of what is foreign (such as pathogen) and determine what is self Not acquired through Action is specific → attack and destroy foreign invaders contact with antigen Goal: prevent pathogens Acquired through an from entering our body individual’s lifetime Immediate and rapid It is mediated by response to a pathogen antibodies or lymphocytes No memory component Has a memory component (i.e, memory cells) General response Respond rapidly to second exposure First and second line of Third line of defense: comes defense into play when the first and Function of Immune System. second line of defense are breached CELLS THAT HELP THE BODY FIGHT INFECTION C. THE THREE LINES OF DEFENSE 1 Macrophage 2 Neutrophil 3 Natural Killer Cell 4 T-cell 5 B-cell DEFINITION OF TERMS The study of molecules, cells, Immunology organs systems and its responses to invading pathogens. Collection of cells, tissues, and Immune system molecules that mediate resistance to infection Three Lines of Defense. Immunity Resistance to disease Invasion → 1st Line → 2nd Line → 3rd Line Body defenses are likened to an army with three lines of Immune Coordinated reaction of cells and defenses. response molecules to infectious microbes Microbio and Para - Mod 4 Immunology 1 1 of 10 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  If the enemy breaks through the first line of defense, it developed uniquely for each microbe will encounter and hopefully be stopped by the second through the action of specialized WBC line of defense. For a particular antigen, our body will If the first two lines of defenses are breached, there’s a respond by producing specific antibodies third line of defense ready to attack it. directed to this particular antigen Specific immune responses improve on repeated exposure to foreign agents such as viruses, bacteria, and toxins Both nonspecific and specific responses usually work together to eliminate pathogenic microorganisms and other foreign agents. II. INNATE IMMUNITY A. FIRST LINE OF DEFENSE FIRST LINE OF DEFENSE 1 Physical Barriers 2 Chemical Barriers 3 Normal microbiota/flora: microorganisms that you normally find in a particular area that do not cause disease. Summary of Host Defenses. 1. PHYSICAL BARRIERS Mucous membrane, Gastrointestinal Tract and 3 LINES OF DEFENSES Genitourinary Tract acts as both a physical and First Innate immunity chemical barrier. Line Defenses present at birth Provide initial protection and blocks PHYSICAL BARRIERS invasion at the portal of entry Keeps microorganisms from penetrating The outermost barrier would be the epithelial cells lining the skin or sterile body components the skin, airways, gastrointestinal tract, and genitourinary Limits access to the internal tissues of tract the body Provide rapid response Usual entry points of Do not involve specific recognition of microorganisms microbe (acts against any type of invading Most microorganisms like agent) bacteria cannot enter intact skin Often perform its function before specific but could enter other openings body defenses are activated of the skin such as the hair Lacks immunologic memory, that is, follicle, sweat, and sebaceous non-specific responses occur at the same glands extent each time a microorganism/foreign Tightly packed Only few microorganisms are body is encountered epithelial cells capable of entering the intact Includes the physical barrier, chemical skin barrier, and normal flora ○ Schistosomiasis: one of the stages in the life cycle of Second Innate immunity Schistosoma is cercaria Line Involves a more internalized system of which has the ability to protective cells and fluids that include penetrate skin. Its lesion is inflammation, phagocytosis, fever, usually found on the lower interferons, and parts of the complement part of the leg. system Acts rapidly at both the local and Periodic shedding systemic levels once the first line of of skin/epithelial Helps remove microbes defense has been breached but the cells protection is still generally non-specific Inhibits the colonization and Consists of the cellular and chemical growth of pathogens systems that comes into play when the first ○ Some bacteria die easily on line of defense is breached dry surfaces Third Adaptive immunity Some microorganisms prefer wet Dry skin Line Highly-specific protection surfaces like fungus Acquired through contact with an ○ If one perspires a lot, he/she infectious agent is more prone to fungal Includes specific host defenses like infections antibodies and lymphocytes that must be The skin have dendritic cells Microbio and Para - Mod 4 🏠 Immunology 1 2 of 10 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  ○ Phagocytic cells that provide polymorphonuclears which non-specific defense against sequesters IRON colonization and infection by Iron is needed by pathogens microorganisms in their metabolism Protective covering: lines the ○ Without it, their ability to eyes, respiratory, GI, and multiply is limited. urinary tracts offers another mode of protection. Saliva (contains hydrolytic It can secrete mucus that can enzymes) cover microbes to be The epithelial cells of the GIT and eliminated. the lower respiratory epithelium ○ The presence of mucus secretes antimicrobial peptides limits bacterial adhesion called defensins, which are GIT to cell surfaces by positively charged amino acids preventing adhesive that can act against Mucous bacterial surface proteins microorganisms by creating holes Membrane (e.g., pilus) from microbial in bacterial cell walls. adhesion. Gastric juices (hydrochloric acid, Helps respiratory tract from enzymes, mucus) pH 1.2 to 3.5 drying out Urine, vaginal secretions, ○ Respiratory tract contains slightly acidic ciliated cells which Lactobacillus acidophilus is a constantly drive mucus normal flora in the genitourinary upward towards the orifices Genitourinary tract that breaks down the Mucus-coated nasal hair Tract glycogen of vaginal secretions helps filter air and help trap into lactic acid making the area microorganisms, dust, and acidic. This aids in warding off pollutants. other microorganisms from colonizing the area. Peristalsis, defecation and GIT vomiting can all rid the body of microbes 3. NORMAL FLORA Genitourinary Long urethra in male (serve as Not an anatomic barrier, but can also block access of Tract distance barrier) pathogens The normal flora of the body can provide microbial antagonism by preventing pathogens from colonizing the 2. CHEMICAL BARRIERS host by: CHEMICAL BARRIERS 1 Competing for nutrients An example is E. coli that can produce Helps flushes bacteriocin, a plasmid-encoded microorganisms from the skin 2 Producing protein, that will inhibit the growth of Has slightly acidic pH harmful other microorganisms (e.g. Salmonella Perspiration Contains certain chemical substances and Shigella). Bacteriocin produces an substances that have adaptive advantage against bacteria, antimicrobial properties like favoring their survival. lysozyme Altering conditions that will affect survival of Also found in tears, saliva, and 3 pathogens nasal secretions Has the ability to dissolve 4. IMPORTANCE OF BARRIERS some bacterial cell walls by Lysozyme The importance of barriers are seen in patients who lost cleaving the bonds between its sugar subunits. them or never had them. With antimicrobial properties A 3rd-degree burn patient will have to be cleaned Lyses bacterial cell wall everyday in the operating room to prevent infection. ○ Everyday the patient suffers the pain of being Keeps the skin from breaking scrubbed and cleaned. Sebum Helps keep the skin pliable and intact An enzyme that produces superoxide radicals, a reactive form Lactoperoxidase of oxygen that is toxic to many microorganisms From activated MQs & PMNs Iron-binding lactoferrins Lactoferrins released by activated macrophages and 3rd-degree burn patient. Microbio and Para - Mod 4 🏠 Immunology 1 3 of 10 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  WHAT HAPPENS DURING ACUTE INFLAMMATION 1 There is mobilization and Localize attraction of immune Infection components to the site of injury An attempt to localize infection 2 Prevent When it reaches the site of injury, it Spread of destroys microbes and block further Microbes invasion 3 Neutralize It neutralizes any toxins produced at Toxins the site of infection 4 When acute inflammation subsides, it sets in motion Repair of mechanisms to repair tissue Cut skin. Damaged damage Tissues Localize and clears away When the microorganism is able to breach the first line harmful substances of defense, microbes enter the host system, leading to the second line of defense. A tissue is inflamed when you see the cardinal signs of inflammation: B. SECOND LINE OF DEFENSE ○ Redness Pathogens that are able to penetrate the first line of ○ Heat defense are usually faced and destroyed by ○ Swelling non-specific cellular and chemical responses of the ○ Tenderness second line of defense. ○ Pain ○ Both the first and the second line of defenses produce nonspecific defense or action against pathogens. The first line of defense is NOT considered a true immune response. However, the second and third line of defenses are part of our immune response. ○ It is where the functions of our immune system takes place, which is to survey, recognize, attack, and destroy pathogens. SECOND LINE OF DEFENSE 1 Inflammation 2 Phagocytosis 3 Fever 4 Interferon Major events of Inflammation. 5 Molecular defenses: complement system 1.2 Chronic Inflammation When neutrophils and macrophages fail to destroy 1. INFLAMMATION microorganisms during an infection An important local defense reaction to tissue injury There is inflammation for more than 2 week May be caused by: Dense infiltration of macrophages and lymphocyte in ○ Pathogen the area ○ Wound The host walls off and isolate at the site of infection ○ Infection where its produces granulomas: ○ Scratching ○ Diseases that granulomas formation may occur: ○ Allergy Schistosomiasis It is a means for body to maintain stability and restore Brucellosis itself Histoplasmosis Tuberculosis 2. PHAGOCYTOSIS Inflammation invites phagocytic cells to the area of injury. PHAGOCYTIC CELLS 1 Monocytes and Macrophages Acute Inflammation. 2 Granulocytes 1.1 Acute Inflammation Neutrophils Eosinophils Microbio and Para - Mod 4 🏠 Immunology 1 4 of 10 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  Basophils Opsonin: any molecule that enhances 3 Dendritic cells phagocytosis (e.g. C3b of complement system and IgG) The most important are the macrophages and neutrophils. 2 Ingestion of microbes Extension of pseudopods by phagocytes around the bacterium to From monocytes 3 Formation of phagocytize the particles → MACROPHAGES Also called Antigen Presenting phagosome. phagosome Cells (APC’s) 4 Fusion of phagosome Most abundant Fusion with lysosome → to form General purpose phagocytes phagolysosome. phagolysosome React early in inflammatory NEUTROPHILS 5 Digestion of microbe Chemicals like lysozymes, response Can leave blood and go to by enzymes lactic acid, nitric oxide, and infected tissues oxidants attack the bacterium. 6 Formation of residual Minor phagocytic role body containing Debris is expelled externally Produces toxic proteins against indigestible material by fusion of phagolysosomes parasites Attracted to sites of parasitic 7 Discharge of waste with cell membrane. EOSINOPHILS infection leading to materials antigen-antibody reaction. E.g. A parasitic infection in patients 2.1 Recognition of Microorganisms by Macrophages will reflect in CBC with increased Recognition of foreign material is one of the most eosinophil. important things in the immune system. Thus, the innate system uses receptors or microbial During an infection, when you look at the CBC of your sensors. patient, you will notice a shift in the WBC where you will find an increase in neutrophils 2.1.1 Pattern Recognition Receptors (PRRs) and Pathogen Associated Molecular Patterns (PAMPs) Collection of protein receptors residing on the ACTIVITIES OF PHAGOCYTES surface of the immune system’s earliest responding 1 Survey tissue compartments for microbes, cells (macrophage and dendritic cell). particulate matter and dead cells Example: Toll-Like Receptors ○ TLRs: PRR that dwell within the cell membrane of 2 Digest and eliminate these material macrophages. ○ One of the TLR is exposed to the environment 3 Extract immunogenic information (antigens) from while the other end resides within the cytoplasm. foreign matter Macrophages or Antigen Presenting Cells (APCs) have PRRs which sense the presence of microorganism through recognition of Pathogen Associated Molecular Patterns (PAMPs) ○ PAMPs: structural features (e.g. LPS, peptidoglycan, proteins, sugars) expressed by microbes. ○ PRR recognition of microbes through PAMPs → phagocytosis. PHAGOCYTES MICROORGANISMS Pattern Recognition Pathogen Associated Receptors (PRRs) Molecular Pattern (PAMPs) Macrophages (APCs) & Structural features Dendritic cells expressed by microbes TLRs (10 Receptors) LPS, peptidoglycans, proteins, sugars, dsRNA Phases of Phagocytosis. Sense presence of STEPS INVOLVED IN PHAGOCYTOSIS microorganisms 1 Chemotaxis and Phagocytes move to a site Adherence of where they are needed. Most of the proteins or antigens on the surface vary microbe to phagocyte Once they reach the area, between different bacteria. by the help of it tries to recognize ○ If the body tried to respond to them, it might opsonin foreign particles like accidentally attack its own proteins. bacteria and binds to it Some molecules/ligands on the surface of the bacteria using an opsonin. are only found on bacteria. Microbio and Para - Mod 4 🏠 Immunology 1 5 of 10 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  There will be certain molecules found on almost every bacterium but not on any normal host body cell TOLL-LIKE RECEPTORS AND THEIR PATHOGENS Ligands are specific to invaders TLR RECOGNIZED MOLECULE PATHOGEN ○ These are the molecules which Toll-Like Receptors will recognize. TLR 1 Lipoprotein unique to bacteria S. aureus ○ They include: Lipopolysaccharides (found on the surface of Lipoteichoic acids Zymosan 1 S. pyrogenes bacteria) TLR 2 (component of fungal cell C. Albicans walls 2 Flagellin (found on the flagellum) TLR 3 Double stranded viral RNA West Nile virus 3 dsRNA (found on viruses) TLR 4 Lipopolysaccharides P. aeruginosae Different TLRs will recognize different examples of these ligands. TLR 5 Flagellin Salmonella When a particular TLR recognizes one, it will trigger a reaction in its cell (e.g. phagocytosis) to break the TLR 7 Single stranded viral RNA HIV invader apart into individual proteins and present them to T cells, turning it into part of the acquired immune TLR 8 Single stranded viral RNA Influenza virus response Alternatively, activation of TLR might lead to the CpG DNA islands found only production of cytokines which are chemical TLR 9 E. coli in bacteria & viruses messengers that triggers an immune response. TLR 10 Unknown Unknown Detection of Foreign Molecule. When a foreign molecule is detected, the TLR dimerizes or joins with the second TLR. The activated TLR sends a signal within the cell to induce production and release of chemicals such as ○ IL-1 and IL-8, to stimulate the inflammatory Cytokines and their function. response. ○ IL-6 and IL-12, to promote specific activities of the 3. FEVER B and T cells. Helps the body contain microorganisms Abnormal elevation of body temperature Systemic response Caused by infections (viruses, bacteria & their toxins) Allergies, cancer, other organic illness Hypothalamus controls body temperature PYROGENS initiate fever & reset the thermostat to a higher level EXOGENOUS ENDOGENOUS Endotoxins from bacteria Interleukin 1 (IL-1) or TLR family and known active ingredients. Tumor Necrosis Factor; which are potent pyrogens There are different TLRs that specifically bind to specific from macrophages molecules of microbes. ○ For example, TLR-4 binds to lipopolysaccharides of Substances from viruses Other substances liberated gram-negative bacteria. by neutrophils and There are about 10 TLRs to date, because these monocytes components are shared among pathogens. Only a small number of TLRs are needed to recognize a variety of microbes. BENEFITS OF FEVER Microbio and Para - Mod 4 🏠 Immunology 1 6 of 10 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  1 Inhibits multiplication of temperature-sensitive microorganisms (i.e. Polioviruses, Herpes virus, Mycobacterium, Syphilis) 2 Impedes nutrition of bacteria by reducing iron availability During fever, macrophages stop releasing iron stores needed by bacterial growth. 3 By virtue of heat produced, it speeds up hematopoiesis and phagocytosis, increases metabolism and stimulates immune reaction Fever is a good defense ONLY up to a certain point because it can lead to death if it spikes up more than 42°C, the patient may go into convulsion and die. 4. INTERFERONS Actions of Alpha and Beta Interferons. Dr Tesoro-Solis’ Interfere with viral replication Immunology Lecture video part 1 They are regulatory cytokines that play a key role in defense against viruses and other intracellular HOW ALPHA AND BETA INTERFERONS WORK pathogens Produced in response to: 1 When viruses bind to receptors of the host cell, a ○ Viral infection signal is sent to the nucleus that directs the cell to ○ Intracellular pathogens (Chlamydiae, Rickettsias, synthesize interferons alpha and beta. Listeria, Toxoplasma gondii) Released by host cells to NON-SPECIFICALLY inhibit 2 Newly synthesized interferons are then secreted the spread of viral infections by the cell into the extracellular space and these NOT viral specific but is effective against a variety of interferons are taken up by uninfected cells by viruses (species specific) binding on to their receptors. The uninfected cells However, they are host specific and are ONLY produce inactive antiviral proteins (AVPs). effective in the same species of host that produce them 3 Meanwhile, the infected cells release viral particles. ○ E.g. Human interferons protect human cells When these new viruses infect an uninfected cell Now known to be used in defense of other microbes and with inactive antiviral proteins, the binding of the in therapy of certain VIRAL INFECTIONS and AVPs with the double-stranded RNA of the virus CANCER triggers the AVP to inhibit viral multiplication by interfering with viral protein synthesis. INF Alpha They do this by degrading the viral mRNA and INF Beta binding to ribosomes thus preventing From infected monocytes, synthesis of viral protein. TYPE 1 In the process, spread of viral infection is macrophages, and lymphocytes Triggered by viral infection inhibited allowing other body defenses to fight Can activate natural killer cells the disease more effectively. INF Gamma 5. COMPLEMENT SYSTEM From NK cell or T cell Another component of the innate immune response TYPE 2 IL-2; IL12 Complements or acts in conjunction with the Play a role in the maturation of B and T antibodies which is part of adaptive immunity Lymphocytes Classical Pathway: the first pathway discovered under the complement system which is triggered by antibodies INF Lambda The sources of complement factors: Inhibits cancer cells ○ Liver (Hepatocytes) TYPE 3 Stimulates B Lymphocytes ○ Lymphocytes Can activate macrophages ○ Monocytes Enhance the activity of phagocytosis Molecular defense Complement immune system in destroying microbes 4.1 Interferon Alpha and Beta Consists of 30 serum proteins that regulate the system: Produced within 5 minutes of cells when the viral ○ Named in the order of their discovery Pathogen associated molecular patterns/PAMPs interact ○ Works to destroy bacteria and certain viruses with certain Pathogen recognition receptors/PRRs like When the complement is activated, it initiates a series of the Toll-like Receptors/TLRs 3,7, and 8 biochemical reactions (or cascade reactions). Microbio and Para - Mod 4 🏠 Immunology 1 7 of 10 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  Alternative Pathway. 5.2 Lectin Pathway Latest and third pathway When macrophages ingest microbes, it releases cytokines that stimulate the liver to produce lectin ○ Lectins: chemicals that bind to mannose, which is a sugar in mannan polysaccharide found on the surfaces of fungi bacteria and some viruses When lectin binds to mannose on the microbial fungal Complement Pathway. cell wall, this binding triggers the activation of C2 and C4 The complement system is activated in three ways: ○ C2 splits to C2a and C2b ○ C4 splits to C4a and C4b ○ When C2a and C4b combine, this activates C3 ACTIVATION OF THE COMPLEMENT SYSTEM C3a initiates inflammation C3b initiates opsonization and phagocytosis, CLASSICAL and eventually cytolysis Antibodies PATHWAY Microbial surface pathogens & ALTERNATIVE pathogenic products (like bacterial PATHWAY endotoxins and glycoproteins) Binds to mannan (Microbial LECTIN polysaccharides or sugar in fungi & PATHWAY some microbes) Activation of the complement system in the innate response proceed via the Alternative and Lectin pathways ○ Both of these pathways are important in the innate system since they do not require antibody activation Classical Pathway: important pathway in the adaptive Lectin Pathway. immunity and this is due to the antibody activation involved in this pathway Destroy microbes: ○ Inflammation ○ Phagocytosis ○ Cytolysis 5.1 Alternative Pathway Discovered second to classical pathway Activated by the presence of microbes There is a hydrolysis of C3 ○ C3 combines with the complement proteins (e.g., factors B, D, and Properdin) on the surface of microbes ○ C3 then splits to C3a and C3b C3a goes on to initiate inflammation via the anaphylatoxins, C5a and C3a. C3b initiates opsonization and cytolysis via the formation of the membrane attack complex Inflammation, Opsonization and Cytolysis. (MAC) and this kills the microbe by making holes in them. Useful in the early stages of infection Microbio and Para - Mod 4 🏠 Immunology 1 8 of 10 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  Whatever the pathway is, the end result is inflammation, opsonization and eventually cytolysis. Macrophages and neutrophils have receptors for In cytolysis, there is a formation of C5b, C6, C7, C8 C3b and can bind C3b coated pathogens. and C9 to form the membrane attack complex which Binding triggers PHAGOCYTOSIS. leads to the cytolysis of the cell. 4 CYTOLYSIS of pathogens via MAC 5.3 Summary of Three Pathways of Complement System C. NATURAL KILLER CELLS ALTERNATIVE LECTIN CLASSICAL Other microbes such as viruses and parasitic worms could be destroyed without being ingested by a Immunity Innate Innate Adaptive defensive cell. They are destroyed extracellularly. Triggered Pathogen Mannose binding Antibody-Antigen Small distinct population of non-phagocytic granular by surfaces (like Lectin binds to Complex binds to LPS, Proteins, mannose/polysac C1(composed of lymphocytes whose main function is to recognize and Cell-wall charides on C1q,C1r,C1s). destroy microbe-infected cells (virus) as well as components) pathogen surface tumor cells. activate the C1q binds to Fc system by of IgG and IgM. triggering cellular TWO WAYS NK CELLS RECOGNIZE TARGET CELLS production of Ab-Ag complex factors B, D and bound to C1 properdin. activates C1s, which cleaves C4 Killer-activating Recognize a number of These factors and C2 to form Receptor different molecules cleave C3 to C4bC2a (c3 generate C3 convertase) 1 convertase Recognize surface markers (C3bBb) Killer-Inhibitory known as MHC (Major Receptor C3bBb cleaves This cleaves C4 Proceed to Histocompatibility Complex I) C3 to C3a (a into C4a and C4b cascade reaction potent and C2 to C2a 2 Fc Receptor that binds to IgG-coated target cells anaphylatoxin) and C2b and C3b C3b binds to C3 C4bC2a (C3 convertase to convertase) form C5 combine convertase (C3bBbC3b) C5 convertase Proceed to cleaves C5 to cascade reaction C5a ( a potent as classical anaphylatoxin) pathway and C5b C5b form complex with C6C7C8C9 (MAC) that leads to cell lysis 5.4 Anaphylatoxins Promote vasodilation and increase vascular permeability Actions of NK cells on healthy host cells and virus-infected They bind to receptor on mast cells and basophils cells. which triggers the latter to release histamines This increases blood flow to site of injury allowing Viruses must get inside the cell in order to replicate. more complement, antibodies and immune cells to enter NK cells are responsible for killing intracellular viruses. the site of infection 5.5 Importance of Complement System COMPONENTS OF NK CELLS IMPORTANCE OF COMPLEMENT SYSTEM 📖 1 Activating receptor 2 Inhibitory receptor 1 Production of ANAPHYLATOXINS 3 Lytic Granules (found inside) 2 Leads to inflammation thru CHEMOTAXIS C5a is an important chemotactic substance that ACTIONS OF NK CELLS ON HEALTHY HOST CELLS can stimulate neutrophils and monocytes to site AND VIRUS-INFECTED CELLS of inflammation Healthy Carry MHC 1 complex 3 OPSONIZATION Host NK cells bind to the host cell by its Cells inhibitory receptor to the MHC 1 Microbio and Para - Mod 4 🏠 Immunology 1 9 of 10 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  complex which inactivates the activating receptor of NK cells Leaves the host cell unaffected Virus- Infection causes the host cell to lose its Infected MHC 1 complex cells Allows NK cells bind to the host cells to a surface protein by means of its activating receptor This stimulates the NK cells to release lytic granules thereby killing the virus-infected cells III. SUMMARY We have an immune system in place that can protect us from infections. The immune system is divided into: ○ Innate immunity: gives initial non-specific protection (1st and 2nd layer of protection). ○ Adaptive immunity: protection is more specific and more long lasting (3rd layer of protection). The 1st defense includes the physical, chemical and normal flora of the body. The 2nd defense includes phagocytosis, inflammation, fever, interferon, natural killer cells and the complement system. Microbio and Para - Mod 4 🏠 Immunology 1 10 of 10 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.