Microbiology RNB 10202 Topic 7.2 Specific Immune System PDF

Microbiology RNB 10202 Topic : Body Defence and immunity Topic 7.2: Specific (Immune system). Prepared by Kogi Introduction Although the second line of defense is very powerful, it does have a some weaknesses: 1. It can’t deal completely with any one particular micro-organism (some pathogen...

Microbiology RNB 10202 Topic : Body Defence and immunity Topic 7.2: Specific (Immune system). Prepared by Kogi Introduction Although the second line of defense is very powerful, it does have a some weaknesses: 1. It can’t deal completely with any one particular micro-organism (some pathogens will nearly always survive this attack) 2. It cannot remember past infections.  This is why a third line of defense is needed Introduction  Our immune system is made up of cells that work with the body’s physical and chemical barriers. It helps prevent any pathogen (disease- causing organism) entering our body.  If the worst comes to the worst and any pathogens do get into our body, the immune system tries to stop them from causing harm.  Our body begin to experience the symptoms of and start suffering from the disease if the pathogens manage to multiply, produce toxins and damage our cells. Learning Outcomes At the end of the session, the student should be able to;  define antibodies and antigen  define immune system  identify organs of the immune system  describe the immune system  describe the different types of B an T lymphocytes  describe the 5 classes of antibodies.  define immunity  explain the different types of immunity Terminology Antigen  Any foreign material, including bacteria, virus or toxins that stimulate an immune response in the body Antibody  A protein that is produced as a result of the immune response to an antigen. Immune  Free from the possibility of acquiring a particular infectious disease  Terminology Humoral immunity  Immunity involving the transformation of B lymphocytes into plasma cell that produce and secret antibodies to a specific antigen. Cell-mediated immunity  An immune response that does not involve antibodies, but involve activation of phagocytes, antigen-specific cytotoxic T-lymphocytes and release of various cytokines in response to an antigen. SPECIFIC DEFENSES THIRD LINE OF DEFENSE : IMMUNE SYSTEM Specific defenses: (3rd Line) Immune system Specific body defences- (3rd line): Immune system What is immune system?  The immune system is a network of cells, tissues, and organs that work together to defend the body against attacks by “foreign” invaders. Organs of the immune system 1. Thymus Greyish, flat, bilobed lymphoid organ Site for development and maturation of T lymphocytes or T cells Weigh 10 g in infant and 3 g in adult 2. Bone marrow The origin site for B lymphocytes or B cells 3. Lymph nodes ◦ Bean shaped clusters Organs of the immune system 4. Spleen 5 inches long Weigh 200 g Traps blood-borne antigens Contain red pulp with erythrocytes, macrophages and white pulp with T lymphocytes 5. Tonsils Posses lymphocytes, macrophages, mast cells and granulocytes Organs of the immune system 6. Peyer's patches Found in the under epithelial layer of intestinal villi Specific body defences- (3rd line) Immune system Functions of the immune system: 1. Differentiate between “self” and “non-self” (“foreign”). 2. Destroy that which is “non-self” Specific body defences- (3rd line) : Immune system  The immune system recognizes, attacks, destroys, and remembers each pathogen that enters the body.  It does this by making specialized cells and antibodies to make the pathogens harmless. Specific body defences – (3rd line): Immune system “Self” and “Nonself”  The key to a healthy immune system is its remarkable ability to distinguish between the body’s own cells, recognized as “self,” and foreign cells, or “nonself.”  To enable the process of identifying “self” and should not be attacked, markers are placed on the outer surface of the body’s own cells.  The marker is a group of molecules called the major histocompatibility complex (MHC) Specific body defences – (3rd line): Immune system- “Self” and “Nonself”  Every person has their own unique MHC. This is the reason why the body recognize and attacked tissue organs donated from others.  The body’s immune defenses normally coexist peacefully with cells that carry distinctive “self” marker molecules.  But when immune defenders encounter foreign cells or organisms carrying markers that say “nonself,” they quickly launch an attack. Specific body defences –(3rd line): Immune system- “Self” and “Nonself”  Anything that can trigger this immune response is called an antigen.  In abnormal situations, the immune system can mistake “self “for “nonself “and launch an attack against the body’s own cells or tissues. The result is called an autoimmune disease. E.g. arthritis and diabetes are autoimmune diseases.  In other cases, the immune system responds to a seemingly harmless foreign substance such as egg. The result is allergy, and this kind of antigen is called an allergen Specific body defences- (3rd line): Immune system  Unlike the first line and second line of defense, the immune system differentiates among pathogens.  For each type of pathogen, the immune system produces cells that are specific for that particular pathogen.  Cells called Lymphocytes are the main players in the immune response system Specific body defences - 3rd line Immune system Lymphocytes  Originate in the bone marrow but migrate to parts of the lymphatic system such as the lymph nodes, spleen, and thymus, Peyer's patches  There are two main types of lymphocytes: ◦ T cells ◦ B cells Specific body defences - 3rd line Immune system A. T cells/T lymphocytes cells  T cells come in different types  They are named T cells after the thymus, an organ situated under the breastbone.  T cells are produced in the bone marrow and later move to the thymus where they mature.  Involved in the cell- mediated response Specific body defences – (3rd line): Immune system Types of T cells 1. Helper T cells (CD4) 2. Cytotoxic T cells or Killer T cell (CD8) 3. Suppressor T cells 4. Memory T cells Specific body defences - 3rd line Immune system- T Cells (cont..) I. Helper T cells (CD4)  Primary task is to activate B cells and killer T cells.  However, the helper T cells themselves must be activated.  This happens when a macrophage or dendritic cell, which has eaten an invader, travels to the nearest lymph node to present information about the captured pathogen. Specific body defences – (3rd line) Immune system – I. Helper T –cell (cont..)  The phagocyte displays an antigen fragment from the invader on its own surface, a process called antigen presentation.  When the receptor of a helper T cell recognizes the antigen, the T cell is activated.  Once activated, helper T cells start to divide and to produce proteins that activate B and T cells as well as other immune cells Specific body defences – (3rd line): Immune system II.Cytotoxic T cells or Killer T cell(CD8)  Specialized in attacking cells of the body infected by viruses and sometimes bacteria.  Also attack cancer cells.  It has receptors that are used to search each cell that it meets. Specific body defences – (3rd line): Immune system II.Cytotoxic T cells or Killer T cell(CD8)(cont..)  If a cell is infected ,it release protein called perforin which forms a pore in target cell, causing lysis of infected cells Diagram showing CytotoxicT Cells Lyse Infected Cells Specific body defences Immune system - T cells (cont..) III. Suppressor T cells  keep the immune system in check so once the infection is controlled, the system is switched off IV. Memory T cells  Remain after the pathogens have been killed to enabling it to response quickly to future infection by the same pathogen Specific body defences -3rd line Immune system B. B cells or B lymphocyte cell :  Formed in the bone marrow.  Migrate to lymphoid organs (lymph node or spleen).  Involved in the humoral response  Produce defensive protein called antibodies in response to antigen Specific body defences -3rd line Immune system - B lymphocyte cell  The B lymphocyte cell searches for antigen matching its receptors.  If it finds such antigen it connects to it, and inside the B cell a triggering signal is set off.  The B cell now needs proteins produced by helper T cells to become fully activated.  When this happens, the B cell starts to divide to produce clones of itself.  During this process, two new cell types are created, plasma cells and B memory cells. Lymphocytes  Diagram showing simplified B cell response Specific body defences Immune system - B cells (cont…) i. The plasma cell  Specialized in producing a specific protein, called an antibody  Antibodies seek out intruders and help destroy them.  Plasma cells produce antibodies at an amazing rate and can release tens of thousands of antibodies per second. Specific body defences Immune system - B cells (cont…) ii. The Memory Cells  The second cell type produced by the division of B cells.  These cells have a prolonged life span and can thereby "remember" specific intruders.  The second time an intruder tries to invade the body, B and T memory cells help the immune system to activate much faster.  The invaders are wiped out before the infected human feels any symptoms. The body has achieved immunity against the invader. Specific body defences Immune system  Antibodies are also called immunoglobulin  Immunoglobulin are classified into five groups 5 classes of antibody 1. Immunoglobulin A (IgA) 2. Immunoglobulin D (IgD) 3. Immunoglobulin E (IgE) 4. Immunoglobulin G (IgG) 5. Immunoglobulin M (IgM) Immunoglobulin classes (Ig) and Functions Ig class Functions IgA Protects the mucous membrane and internal cavities against infection (provides immunity to infant digestive tract). Found in tears, saliva, colostrum and other secretions Self-life in serum: 6 days IgE Causes allergies, drug sensitivity, anaphylaxis and immediate hypersensitivity Fight against parasitic disease Found on surfaces of basophil and mast cells Self-life in serum: 2 days Immunoglobulin classes (Ig) and Functions Ig class Functions IgD In serum function is unknown. On B cell surface, initiate immune response Found in B-cell surface, blood, and lymph Self-life in serum: 3 days IgM First antibodies produced during an infection. Effective against microbes and agglutinating antigens. Found in Blood, lymph, B cell surface Self-life in serum: 5 days IgG Enhances phagocytosis, neutralizes toxins and viruses, protects fetus and newborn. Found in Blood, lymph, intestine Self-life in serum: 23 days Can be transferred through placenta Diagram shows the amplification of the inflammatory response—in this e.g., an antibody-mediated response to a bacterial attack. Plasma cells release antibodies, which travel through the blood and mark the attackers. These marked invaders set other defense elements such as macrophages into action, enabling them to participate in the defense. Consequences of Antibody Binding Overview of the Immune Response TYPES OF IMMUNITY Learning Outcomes At the end of the session, the student should be able to;  define immunity  describe the different types of immunity  identify ways of acquiring different types of immunity  identify different types of vaccine IMMUNITY Definition  Immunity is the state of protection against infectious disease obtained either through an immune response generated by immunization or previous infection, or by other non-immunological factors.  IMMUNITY INNATE ACQUIRED/ (genetic, inborn ADAPTIVE NATURALLY ACQUIRED ARTIFICIALLY ACTIVE ACQUIRED Protection acquired by getting ACTIVE the disease Protection acquired by immunization with vaccine that stimulate PASSIVE PASSIVE the body to actively Protection Antibodies passively acquired by direct produce own antibody cross from mother to injection of baby via placenta or antibodies breast milk (immunoglobulin)) Acquired Immunity  Acquired immunity result from the active production or receipt of antibodies. Types of immunity Definition 1. Innate immunity ◦ The nonspecific first line of defence against foreign pathogens that is an integral facet of the immune response, which is mediated by dendritic cells (DCs), natural killer (NK) cells, macrophages, neutrophils, basophils, eosinophils and mast cells. Types of immunity Innate immunity (.. cont)  Sometimes referred to as genetic or inborn  Present from birth and are effective against potentially infective agent.  Do not depend on having previous experience with any particular microorganism Types of immunity 2. Adaptive immunity Definition  Protection from an infectious agent that is mediated by B and T Lymphocytes following exposure to specific antigen and characterized by immunological memory Types of immunity (Cont..) 2. ADAPTIVE IMMUNITY (…cont) ◦ Not present at birth ◦ Develop during our life ◦ Acquired immunity (immunity that result from active production or receipt of antibodies) can be achieved: a. naturally b. artificially Types of immunity (cont…) A. Naturally acquired  Can be gained passive or active i. Naturally Passive Acquired Immunity ◦ Immunity or resistance acquired as a result of a receipt of antibodies produce by another person or by animal (such protection usually temporary).  E.g. : IgG – transfer from mother to fetus across the placenta IgA - transfer from mother to baby in milk during feeding Types of immunity (cont…) A. Naturally acquired….cont.. ii. Naturally Active Acquired Immunity ◦ Result from the production of antibodies by the immune system in response to the presence of an antigen (produce within own body- usually long lasting). ◦ Occurs after exposure to an infectious organism (antigen). Types of immunity A. Naturally acquired … cont.. ii. Natural Acquired Active immunity …cont..  Antigen stimulate the immune system to produce specific antibodies and memory cells to ward off future encounters with same pathogen. ◦ E.g. after exposure to measles, mumps or chicken pox.  Usually long lasting Types of immunity (cont..) B. Artificially acquired ◦ Can be obtained by injection of vaccines ◦ Can be active and passive i. Artificially Acquired Active immunity  An antigen introduced during vaccination stimulate cell-mediated and antibody- mediated immune responses leading to production of memory cells ◦ E.g. of vaccines; Bacille Calmette-Guerin (BCG) – given against Tuberculosis.  May last long, or long life. Types of immunity (cont…) B. Artificially acquired …cont.. ii. Artificial Acquired Passive Immunity  Intravenous injection of immunoglobulins (antibodies) from human or animal  Does not produced antibodies and memory cells; e. g. Antiserum, Antitoxin, Gamma globulin  Immunity is short lived and offers only immediate, short term protection  Types of Acquired Immunity ACTIVE PASSIVE Natural Artificial Natural Artificial Clinical or Vaccines Congenital Antiserum subclinical Inactivated (across Antitoxin clinical (Killed) placenta) Gamma pathogen Colostrum globulin Attenuated (weakened) pathogens Extracts (parts of pathogen) summary  Ways of acquiring artificially active and passive immunity Vaccines  Vaccines is an antigenic materials when introduced into the body it stimulate the specific antibodies against a specific microorganism. Vaccines can be: 1. Attenuated microbes. ◦ These are living, non-virulent strains of a microbe Examples of vaccines that contain attenuated microbes include:  the MMR vaccine containing attenuated measles, mumps and rubella viruses;  oral polio vaccine containing attenuated poliomyelitis viruses  Bacille Calmette-Guerin (BCG) – given against Tuberculosis. Vaccines 2. killed organisms, fragmented microorganisms, or antigens produced by recombinant DNA technology a. Examples of vaccines containing killed or inactivated microbes include: ◦ the rabies vaccines containing whole, killed rabies viruses; ◦ the influenza vaccines consist of inactivated influenza viruses, either whole or broken down Vaccines b. Fragments of microorganisms e.g. immunizations against:  Hemophilus influenzae type b. Vaccine C. Recombinant DNA technology include:  Hepatitis B vaccine (HepB),  Diphtheria, tetanus, acellular pertussis (or whooping cough) vaccine (DTAP);  Hepatitis A vaccine (HepA);  Cervarix, the vaccine against human papilloma virus (HPV) types 16 and 18  Recombinant DNA is a DNA that has been created artificially. DNA from two or more sources is incorporated into a single recombinant molecule. Vaccine 3. Toxoid  An exotoxin that has been treated to be nonpoisonous but still capable of stimulating an immune response against the natural exotoxin  The body responds by making antibodies capable of neutralizing the exotoxin. Examples of vaccines containing toxoids include: ◦ diphtheria and tetanus Passive artificially acquired immunity I. Immune globulin (IG) an antibody- containing serum obtained from another person: E.g. include:  Human hepatitis B immunoglobulin (HBIG) to prevent hepatitis B in those not actively immunized with the help of vaccine; ◦ For e.g. A nurse who has accidentally exposure to hepatitis B virus via a needlestick injury and does not have immunity, may receive hepatitis B immunoglobulin in an attempt to provide instant protection from virus. Passive artificially acquired immunity Antiserum: Serum containing antibodies to a specific antigen(s). ◦ Obtained from injecting an animal (horse, rabbit, goat) with antigen (snake venom, botulism or diphtheria toxin).  Passive immunity provides immediate but temporary protection.  Types Of Vaccine Types of Vaccine Examples Live (attenuated) Adenovirus, measles, (rubeola), mumps, virus German measles (rubella), polio (oral), small pox (varicella), yellow fever. Dead (incativated) Hepatitis B, influenza, Japanese viruses or viral encephalitis, polio, rabies antigens Live (attenuated) BCG, typhoid fever bacteria Bacterial capsular Hib (for protection against antigens Heamophilus influenzae type b), meningococcal, pneumococcal Bacterial Toxoids Diphtheria, tetanus