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Body defense mechanism and immunity

The term immunity refers to the body’s specific protective response to an invading foreign agent or organism.

The human body has the ability to resist almost all types of organisms or toxins that tend to damage the tissues and organs. The capability is called immunity.

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Body defense mechanism and immunity

  1. 1. Body defense mechanism & Immunity Shrooti Shah M.Sc. Nursing Batch 2011 Page 1
  2. 2. Objectives1. Define immunity2. Classify immunity3. Explain mechanisms of natural and acquired immunity4. Discuss the response to invasion by microorganisms.5. Describe abnormal immune response6. Discuss nursing process related to immune system Page 2
  3. 3. Immunity• The term immunity refers to the body’s specific protective response to an invading foreign agent or organism.• The human body has the ability to resist almost all types of organisms or toxins that tend to damage the tissues and organs. The capability is called immunity. Page 3
  4. 4. Types of immunity 1. Natural (Innate) immunity2. Acquired (adaptive) immunity Page 4
  5. 5. Natural and acquired immunity Natural immunity Acquired immunity1. Is a nonspecific 1. Specific immunity immunity present at birth develops after birth2. responses to a foreign 2. Increases in intensity invader are very similar with repeated exposure from one encounter to to the invading agent. the next. Page 5
  6. 6. Natural (Innate immunity)• The basis of natural defense mechanisms is the ability to distinguish between friend and foe or self and non-self.• Such natural mechanisms include 1. Physical and chemical barriers – Skin and mucous membrane – Antimicrobial substance in body secretions 2. The action of WBCs 3. Inflammatory response. Page 6
  7. 7. Physical and chemical barriers Skin and mucous membrane• When skin and mucous membrane are intact and healthy they provide a physical barrier to invading microbes.• Sebum and sweat secreted on to the skin surface contains antibacterial and antifungal substances.• Hairs in the nose acts as a coarse filter.• One way flow of urine from the bladder during Page 7 micturation
  8. 8. Antimicrobial substance in body secretions1. Hydrochloric acid in gastric juice2. Lysosomes3. Saliva4. Immunoglobulin in nasal secretions and saliva5. Interferons Page 8
  9. 9. White blood cell action• WBCs participate in both the natural and the acquired immune responses.• Granulocytes include neutrophils, eosinophils and basophils.• Nongranular leucocytes include monocytes or macrophages and lymphocytes.• Lymphocytes consisting of B cells and T cells, play major role in humoral and cell mediated immune responses. Page 9
  10. 10. Inflammatory response• Major function of the natural (non specific or innate) immune system.• Chemical mediators assist this response by minimizing blood loss, walling off the invading organism, activating phagocytes and promoting formation of fibrous scar tissue and regeneration of injured tissue Page 10
  11. 11. Dysfunction of the natural immune system• Immunodeficiency• Persistent inflammatory response• Autoimmune bodies Page 11
  12. 12. Acquired immunity• Usually develops as a result of prior exposure to an antigen through immunization or by contracting a disease.• Weeks or months after exposure to the disease or vaccine, the body produces an immune response that is sufficient to defend against the disease upon re-exposure to it. Page 12
  13. 13. Active and passive immunity1. Active immunity: Active immunity means that the individual has responded to an antigen and produced his own antibodies, lymphocytes are activated and the memory cells formed provide long lasting resistance.2. Passive immunity: In passive immunity the individual is given antibodies produced by someone else Page 13
  14. 14. Response to invasion• When the body is invaded or attacked by bacteria, viruses, or other pathogens, it has three means of defending itself: 1. The phagocytic immune response 2. The humoral or antibody immune response 3. The cellular immune response Page 14
  15. 15. Phagocyte immune response• The first line of defense• Involves the WBCs (granulocytes and macrophages), which have the ability to ingest foreign particles.• Phagocytes also remove the body’s own dying or dead cells. Page 15
  16. 16. Humoral and cellular immune response• A second response, the humoral immune response (sometimes called the antibody response), begins with the B lymphocytes, which can transform themselves into plasma cells that manufacture antibodies.• The third mechanism of defense, the cellular immune response, also involves the T lymphocytes, which can turn into special cytotoxic (or Killer) T cells that can attack the pathogens themselves. Page 16
  17. 17. Humoral immune response1. Before exposure to a specific antigen, the clones of B lymphocytes remain dormant in the lymphoid tissue.2. On entry of a foreign antigen, macrophages in the lymphoid tissue phagocytize the antigen and then present it to adjacent B lymphocytes.3. In addition, the antigen is presented to T cells at the same time, and activated helper T cells are formed.4. Those B lymphocytes specific for the antigen immediately enlarge and take on the appearance of lymphoblasts. Page 17
  18. 18. Humoral immune response cont…5. Some of the lymphoblasts further differentiate to form plasmablasts, which are precursor of plasma cells.6. The mature plasma cells then produces gamma globulin antibodies.7. Other B lymphocytes differentiate into B- lymphocyte clones with a memory for the antigen. Page 18
  19. 19. Primary response and secondary response Primary response Secondary response1. Response for forming 1. Response that occurs antibodies that occur on after second exposure to first exposure to a the same antigen. specific antigen.2. Appears 1 week after, 2. Begins rapidly after with weak potency and exposure to the antigen short life (often within hours) is far more potent, and forms antibodies for many months rather than for only a few weeks. Page 19
  20. 20. Role of antibodies
  21. 21. Antibodies• The antibodies can inactivate the invading agent in one of the several ways, as follows:1. Agglutination: in which the multiple large particles with antigens on their surface.2. Precipitation: in which the molecular complex of soluble antigen and antibody becomes so large that it is rendered insoluble and precipitates.3. Neutralization: in which the antibodies cover the toxic sites of the antigenic agent.4. Lysis: in which some potent antibodies are occasionally capable of directly attacking membranes of cellular agents and thereby cause rupture of the agent. Page 21
  22. 22. Types of immunoglobulin
  23. 23. IgG IgG (75% of total immunoglobulin)• Appears in serum and tissues (interstitial fluid)• Assumes a major role in bloodborne and tissue infections.• Activates the complement system.• Enhances phagocytosis• Crosses the placenta Page 23
  24. 24. IgA IgA (15% of total immunoglobulins)• Appears in body fluids (blood, saliva, tears, breast milk, and pulmonary, gastrointestinal, prostatic and vaginal secretions).• Protection against respiratory, gastrointestinal and genitourinary infections.• Prevents absorption of antigens from food.• Passes to neonate in breast milk for protection. Page 24
  25. 25. IgM IgM (10% of total immunoglobulins)• Appears mostly in intravascular serum• Appears as the first immunoglobulin produced in response to bacterial and viral infections.• Activates the complement system. Page 25
  26. 26. IgD IgD (0.2% of immunoglobulins)• Appears in small amounts in serum• Possibly influences B-lymphocytes differentiation , but role is unclear. IgE IgE (0.004% of immunoglobulins)• Appears in serum• Takes part in allergic and hypersensitivity of reactions• Combats parasitic infections. Page 26
  27. 27. Cellular immune response• These develop gradually over a period of 24 to 48 hours after the second encounter with an antigen.• T lymphocytes are primarily responsible for cellular immunity.• Stem cells continuously migrate from the bone marrow to the thymus gland, where they develop into T cells.• By spending time in the thymus, these cells are programmed to become T cells rather than Page 27 antibody producing B lymphocytes.
  28. 28. Cellular immune response cont…• T cells attack foreign invaders directly. Cellular reactions are initiated by the binding of an antigen with an antigen receptor .• The T cells then carry the antigenic message, or blue print, to the lymph nodes, where the production of other T cells is stimulated.• Some T cells remain in the lymph nodes and retain a memory for the antigen. Other T cells migrate from the lymph nodes into the general circulatory system and ultimately to the tissues. Page 28
  29. 29. Types of T cells1. Helper T cells:• When activated, helper T cells secrete cytokines that attract and activate B cells, cytotoxic T cells, natural killer cells, macrophages and other cells of the immune system.• Helper T cells produce different types of cytokines and determine whether the immune response will be the production of antibodies or cell mediated immune response. Page 29
  30. 30. 2. Cytotoxic T cells• Cytotoxic T cells is a direct attack cell that is capable of killing micro-organisms and, at times, even some of the body’s own cells.• For this reason these are called killer cells.• Cytotoxic attack the antigen directly by altering the cell membrane and causing cell lysis and releasing cytolytic enzymes and cytokines. Page 30
  31. 31. 3. Supressor T cells• They are capable of suppressing the functions of both cytotoxic and helper T cells.• It is believed that these suppressor functions serve the purpose of preventing the cytotoxic cells from causing excessive immune reactions that might be damaging to the body’s own tissues. Page 31
  32. 32. Complement system• Circulatory plasma proteins which are made in the liver and activated when an antibody couples with its antigen, are known as complement.• Complement has three major physiological functions: a. defending the body against bacterial infection b. bridging natural and acquired immunity c. disposing of immune complexes and the byproducts associated with inflammation. Page 32
  33. 33. Complement systemComplement mediated immune response are summarized as:1. Cytolysis: Lysis and destruction of cell membranes of body cells or pathogens.2. Isosonization: Targeting of the antigen so that it can be easily engulfed and digested by the macrophages and other phagocytic cells.3. Chemotaxis: chemical attraction of neutrophils and phagocytic cells to the antigen.4. Anaphylaxis: activation of mast cells and basophils with release of inflammatory mediators that produce smooth muscle contraction and increased vascular permeability. Page 33
  34. 34. Abnormal immune reactions1. Antibody mediated2. Cell-mediated3. Mixed antibody Page 34
  35. 35. Antibody mediated reactions• These occur within minutes of exposure to an allergen (antigen).• The most common manifestations of this type of allergic reaction include: food allergies, childhood eczema, hay fever, extrinsic asthma.• In these conditions the released chemicals act locally, causing different effects that depend on the site. Page 35
  36. 36. Acute systemic anaphylaxis (anaphylactic shock)• It is caused by the entry of an allergen into the blood e.g. snake venom, injectable penicillin.• There are profound effects throughout the body, including generalized vasodilatation, leading to severe hypotension and contraction of smooth muscle in the respiratory tract, causing acute breathing difficulties. Page 36
  37. 37. Other antibody mediated reactions:• Reaction of antibodies with cells that have antigens on their cytoplasmic membranes may cause the cells to rupture.• Abnormal reactions to antibody/antibody complexes sometimes result in them adhering to the endothelium of blood vessels causing inflammation and local damage.. Page 37
  38. 38. Cell mediated reactionsThe antigen include:1. Intracellular microbes, e.g. those causing tuberculosis, measles, mumps.2. Some vaccines, e.g. against smallpox.3. Some metals and compounds that combine with protein in the skin and cause allergic contact dermatitis. Page 38
  39. 39. Mixed reactionsAutoimmune diseases:• Tissue damage and signs of disease as the body fails to recognize its own tissues. Destruction of the body’s own cells may be either humoral or cell-mediated. – Thyroid- Hashimoto’s thyroiditis – Stomach- Addisonian pernicious anemia – Cortex of the adrenal gland- addison’s disease. – Pancreas-type I diabetes mellitusOrgan transplantation and rejection Page 39
  40. 40. Nursing processNursing assessment• An assessment of immune function begins with a health history and physical examination Health history 1. Age 2. Nutrition 3. Infection and immunization 4. Allergy 5. Medications and blood transfusion 6. Lifestyle and other factorsPhysical examination Page 40
  41. 41. Nursing management• Assisting with medical measures aimed at improving immune status and treating infection, improving the nutritional status, and maintaining bowel and bladder function.• Careful hand hygiene, encouraging the patient to cough and perform deep-breathing exercises at regular intervals, and protecting the integrity of the skin and mucous membranes.• Use strict aseptic technique when performing invasive procedures Page 41
  42. 42. Nursing management cont…• Assisting the patient in managing stress and in adopting a lifestyle that enhances immune system function.• The patient or parents (if the patient is a child) must be informed about the potential risks and benefits of the treatment regimen.• A major role of the nurse is to assist the patient and family to understand the treatment options and to cope with the uncertainties of treatment outcomes. Page 42
  43. 43. Health education• About the signs and symptoms that indicate infection.• Whenever they experience a symptom that is not typical for them, they should contact their health care provider.• About any prophylactic medication regimen, including dosage, indications, times, actions, and side effects.• Avoid others with infections and crowds. Page 43
  44. 44. Health education cont…• The patient and family also need to learn about other ways to prevent infection.• Instructed to monitor for subtle changes in physical status and must be informed of the importance of seeking immediate health care if changes occur.• About the importance of continuing the treatment regimen and assisted in incorporating it into their lives. Page 44
  45. 45. References1. Wilson KJW, Waugh A. Ross and Wilson Anatomy and physiology in Health and illness. Eigth edition. NewYork; Churchill Livingstone:1998.2. Smeltzer SC, Bare B. Textbook of Medical surgical Nursing. 10th edition. Philadelphia; Lippincott Williams and wilkins: 2004.3. Guyton AC, Hall JE. Textbook of Medical Physiology. Eleventh edition. Philadelphia; Saunder (Elsevier) : 2006. Page 45