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Defense Mechanism (2).pptx

  1. 1. Subject: Microbiology Faculty: Waheed Ahmed Mugheri, Nursing Lecturer Sindhu College Of Nursing Khairpur, Post-RN BSc.N D.U.H.S Karachi.
  2. 2. At the end of this session…….  The students will be able to…  To know about body defense system.  To know about Immune system.  To know about different types of immunity.  To know about different lines of defense. mechanism.  To know about some terminologies.
  3. 3. Define: Defense Mechanism It is defined as body fights against diseases by keeping things out of your body that are foreign bodies and also maintain physical health. Your primary defense against pathogenic germs are physical barriers like your skin. Our body is also produce pathogen-destroying chemicals, like lysozyme, found on parts of your body without skin, including your tears, saliva, and mucus membranes.
  4. 4. 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.  The reaction by the immune system to antigens (substances such as bacteria and viruses) that the body recognizes as foreign is called immune response.  The immune system protects the body from possibly harmful substances by recognizing and responding to antigens.
  5. 5. Some Important Terminologies…..  Immunity  Antigen  Pathogen  Antibodies  Vaccine  Immunization  Phagocytosis
  6. 6. Terminologies Immunity: It is the ability of an organism to resist a particular infection or toxin by the action of specific antibodies or sensitized white blood cells. Antigen: It is a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies. E.g. Virus, Bacteria, fungi, protozoa & parasite. Pathogen: A pathogen is usually defined as a harmful microorganisms which causes diseases to human or host.
  7. 7. Conti….  Antibodies: A protein made by plasma cells (a type of white blood cell) in response to an antigen (a substance that causes the body to make a specific immune response). Immunization: A process by which a person becomes protected against a disease through vaccination. This term is often used interchangeably with vaccination. Vaccine: It is an antigenic substance, which used to stimulate the production of antibodies and provide immunity against one or several diseases, prepared from the causative agent of a disease, either killed or live form.
  8. 8. Conti…. Phagocytosis: It is a process by which certain living cells called phagocytes ingest or engulf other cells or particles. The phagocyte may be a free-living one-celled organism, such as an amoeba, or one of the body cells, such as a white blood cell.
  9. 9. Main Parts of Immune System  The main parts of the immune system are: white blood cells, antibodies, the complement system, the lymphatic system, the spleen, the thymus, and the bone marrow.
  10. 10. Types of immunity
  11. 11. Conti……
  12. 12. Conti….
  13. 13. Innate Immunity Innate or nonspecific: It is defined as the defense system with which we were born. It protects us against all antigens. Innate immunity involves barriers that keep harmful materials from entering your body.  Immunity that is naturally present and is not due to prior sensitization to an antigen. In the innate immune response, these include macrophages, neutrophils, eosinophils, basophils, mast cells, and dendritic cells.
  14. 14. Physical Parameters/Barriers Fish scale: A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most fishes is covered with these protective scales. Mucous: The mucosal immune system is the largest component of the entire immune system, having evolved to provide protection at the main sites of infectious threat. Skin: The skin has an immune system that protects the body from infection, cancer, toxins, and attempts to prevent autoimmunity, in addition to being a physical barrier against the external environment.
  15. 15. Cellular Parameters/Barriers  Cellular immunity: It occurs inside infected cells and is mediated by T lymphocytes. The pathogen's antigens are expressed on the cell surface  Macrophages: Macrophages are scavengers whose job is to engulf or eat up infecting germs and even infected cells. Macrophages also help to overcome infection by secreting signals that help activate other cell types to fight against infections. o Macrophages are a type of white blood cell (Monocyte) that are part of your body's defense mechanism and also part of the immune response in asthma.  Granulocytes: As part of the immune response, granulocytes migrate to the site of infection and release a number of different effector molecules, including histamine, cytokines, chemokines, enzymes and growth factors. o It is a white blood cell with secretory granules in its cytoplasm. E.g. Neutrophil, Basophil & Eosinophil.
  16. 16. Conti…. Neutrophil: are the most abundant type of granulocytes and make up (40% to 70%) of all white blood cells in humans.  A type of immune cell that is one of the first cell types to travel to the site of an infection. It helps in fight against infections by ingesting microorganisms. Basophil: Normally, basophils account for (0.5% to 1%) of your white blood cell count. They play a part in "immune surveillance". This means they have the ability to help detect and destroy some early cancer cells. Another important function of basophils is that they release the histamine in their granules during an allergic reaction & asthma attack. Eosinophils: (1.0 to 4.0 % )of your blood. It is a type of disease-fighting white blood cell. This condition most often indicates a parasitic infection, an allergic reaction or cancer.
  17. 17. Conti…. Dendritic cells: These (DC) are among the first cells to encounter pathogens or damage in peripheral tissues and upon activation, DCs migrate to lymph nodes where they activate and educate T- Lymphocyte cells to initiate the immune response. B-Cells: These are also known as B- Lymphocyte cells. B-cells fight bacteria and viruses by making Y-shaped proteins called antibodies, which are specific to each pathogen and are able to lock onto the surface of an invading cell and mark it for destruction by other immune cells. o B cells are produced in stem cell of bone marrow and also mature their. o B cells fight bacterial infections specially.
  18. 18. Conti….  T.Cells: These cells are part of the immune system and develop from stem cells in the bone marrow & mature in thymus. They help protect the body from infection and may help fight cancer & also called T lymphocyte  The T cells respond to viral infections and boost immune function of other cells.  There are two types of T.Lymphocyte 1) Killer T cells (Recognizes and kills virally infected cells and tumours) CD8 cells can kill cancer cells and other invaders. 2) Helper T cells (helps in activation of B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.) CD4 cells lead the fight against infections. o Note: T & B Lymphocytes cells are part of adaptive immunity
  19. 19. Conti…  Mast Cells: A mast cell (also known as a mastocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a part of the immune and neuroimmune systems.  Natural killer cells: (NCCs: Nonspecific Cytotoxic Cells) A type of immune cell that has granules (small particles) with enzymes that can kill tumor cells or cells infected with a virus. A natural killer cell is a type of white blood cell & also known as NK cell o Heparin: It triggers their immune system and causes a reaction where antibodies form and activate platelets, these are tiny blood cells that clump together to form clots and stop bleeds in your body. o Histamine: It is produced by basophils and by mast cells found in nearby connective tissues.  Histamine is involved in the inflammatory response and has a central role as a mediator of itching. As part of an immune response to foreign pathogens.
  20. 20. Humoral Parameters/Barriers  It is also called antibody-mediated immunity. With assistance from helper T cells, B cells will differentiate into plasma B cells that can produce antibodies against a specific antigen. The humoral immune system deals with antigens from pathogens that are freely circulating, or outside the infected cells.  Transferrin: It is also associated with the innate immune system. It is found in the mucosa and binds iron, thus creating an environment low in free iron that impedes bacterial survival in a process called iron withholding. o Transferrin: A plasma protein that transports iron through the blood to the liver, spleen and bone marrow.  Lysozyme: It is a cornerstone of innate immunity. The degradation and lysis of bacteria by Lysozyme enhance the release of bacterial products, including PG, that activate pattern recognition receptors in host cells. o Lysosome enzymes are made by proteins from the endoplasmic reticulum and enclosed within vesicles by the Golgi apparatus.
  21. 21. Conti…. Lectins: They are known to play important roles in the innate immune system. It helps mediate the first-line defense against invading microorganisms. Cytokines: Cytokines are small proteins that are crucial in controlling the growth and activity of other immune system cells and blood cells. When released, they signal the immune system to do its job.
  22. 22. Conti…. Compliments: The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism. It is part of the innate immune system. The complement system consists of a number of small proteins found in the blood, made by the liver. o Functions of the complement system: 1) The activation of inflammation. 2) The opsonization (labeling) of pathogens and cells for clearance/destruction. 3) The direct killing of target cells/microbes by lysis.
  23. 23. Define Antibodies These are made up of protein by plasma cells (a type of white blood cell) in response to an antigen (a substance that causes the body to make a specific immune response). Each antibody can bind to only one specific antigen.
  24. 24. Types of Antibodies  Following are the types of antibodies: 1) Immunoglobin (IgG). 2) Immunoglobin (IgM). 3) Immunoglobin (IgA). 4) Immunoglobin (IgE). 5) Immunoglobin (IgD).
  25. 25. Conti…. Immunoglobin.G: It is the most abundant antibody isotype in the blood (plasma), accounting for 70-75% of human immunoglobulins (antibodies). IgG detoxifies harmful substances and is important in the recognition of antigen-antibody complexes by leukocytes and macrophages. IgG is transferred to the fetus through the placenta and protects the infant until its own immune system is functional. Immunoglobin.M: It usually circulates in the blood, accounting for about 10% of human immunoglobulins. IgM has a pentameric structure in which five basic Y-shaped molecules are linked together. B cells produce IgM first in response to microbial infection/antigen invasion. Although IgM has a lower affinity for antigens than IgG, it has higher avidity for antigens because of its pentameric/hexameric structure. IgM, by binding to the cell surface receptor, also activates cell signaling pathways.
  26. 26. Conti…. Immunoglobin.A: IgA is abundant in serum, nasal mucus, saliva, breast milk, and intestinal fluid, accounting for 10-15% of human immunoglobulins. IgA in breast milk protects the gastrointestinal tract of neonates from pathogens. Immunoglobin.E: IgE is present in minute amounts, accounting for not more than 0.001% of human immunoglobulins. Its original role is to protect against parasites. In regions where parasitic infection is rare, IgE is primarily involved in allergy. Immunoglobin.D: IgD accounts for less than 1% of human immunoglobulins. IgD may be involved in the induction of antibody production in B cells, but its exact function remains unknown.
  27. 27. Difference B/W Adaptive & Innate Immunity Innate Immunity Adaptive Immunity It is basic resistance & present by birth, also first line defense against infections. This develops during life time. In this immunity present after birth by naturally & artificially. Prevents the entry of pathogen or acts within hours of antigen appearance in the body. Antigen specific immune response and antigen recognition by this system, makes immune cells specifically designed to attack that antigen. First line defense, Physical barriers( Skin, mucous linings, saliva, tears, stomach) Immune cells ( NK cells, macrophages, neutrophils, dendritic cells, mast cells), that attacks foreign cells in the body. T & B lymphocytes, antibodies, classical complement pathway.
  28. 28. Continue Contact or exposure with antigen or antigen is not essential (Antigen independent). Contact or exposure with pathogen or antigen is essential (Dependent). Rapid response with in hours, effector molecules (Cytokines) Slow response takes days/weeks, but may be long lasting and also life long, Effector molecules (Antibodies). No immunologic memory similar response on repeated exposure. Immunologic memory, future response against a specific antigen is more efficient. Innate immunity is involved in all levels of immune response. Adaptive response is mounted when innate response signals for serious infection.
  29. 29. Difference B/W Humoral and Cell mediate Immunity
  30. 30. Define Hypersensitivity  Hypersensitivity: It is also called hypersensitivity reaction or intolerance. Refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity.  They are usually referred to as an over-reaction of the immune system and these reactions may be damaging and uncomfortable.
  31. 31. Types of hypersensitivity:  The four types of hypersensitivity are:  Type I: reaction mediated by IgE antibodies.  Type II: cytotoxic reaction mediated by IgG or IgM antibodies.  Type III: reaction mediated by immune complexes.  Type IV: delayed reaction mediated by cellular response. 
  32. 32. Immediate Hypersensitivity  Immediate hypersensitivity (type I) is also known as immediate contact urticaria and the reaction occurs very rapidly. Common causes include insect bites and ingested peanuts. It is mediated by IgE antibodies, which bind to the surface of mast cells.  It is an allergic reaction provoked by re- exposure to a specific type of antigen referred to as an allergen.
  33. 33. Delayed Hypersensitivity  Delayed-type hypersensitivity (DTH) is defined as the recruitment of T cells into tissues to be activated by antigen-presenting cells to produce cytokines that mediate local inflammation. CD8+ T cells are now known to mediate DTH responses in allergic contact dermatitis, drug eruptions, asthma, and autoimmune diseases.
  34. 34. Define Resistance  It is defined as the natural or genetic ability of an organism to avoid or repel attack by biotic agents (pathogens, pests, parasites, etc.) or to withstand the effects of abiotic agents.
  35. 35. Define Susceptibility  It is defined as the quality or state of being susceptible especially : lack of ability to resist some extraneous agent (such as a pathogen or drug)  Susceptibility is being easily affected by something.  E.g: Susceptibility is having a very weak immune system which causes a person to frequently get colds.
  36. 36. Role Of Memory, Tolerance & Specificity  Memory: Memory is defined by the persistence of specific lymphocytes and antibody-producing plasma cells rather than that of antigen to induce continuous lymphocyte activation. • E.g: When an individual recovers from chickenpox, the body develops a memory of the infection that will specifically protect it from the causative agent, the varicella-zoster virus, if it is exposed to the virus again later.  Tolerance: It is a state of unresponsiveness of the immune system to substances or tissue that have the capacity to elicit an immune response in a given organism. Tolerance is the prevention of an immune response against a particular antigen. • E.g: Induced tolerance is a deliberate manipulation of the immune system to avoid the rejection of transplanted organs or to provide protection from allergic reactions.
  37. 37. Conti….  Specificity: It is defined as the quality or condition of being specific, such as the condition of being peculiar to a particular individual or group of organisms host specificity of a parasite.