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OVERVIEW OF THE IMMUNE SYSTEM AND BODY'S DEFENCE SYSTEM.pdf
- 1. Definition of terms ➢Immunology ➢The study of the immune system or immunity ➢the study of all aspects of host defense against infection and of adverse consequences of immune responses. ➢The study of the physiological mechanisms which enable the body to recognize materials as foreign and to neutralize, metabolize or eliminate them without injury to the host tissue.
- 2. cont… Immunity ➢State of protectionfrom infectious diseases Immune system ➢ A remarkably versatile defense system that has evolved to protect animals from invading pathogenic microorganisms and cancer. ➢ It is able to generate an enormous variety of cells and molecules capable of specifically recognizing and
- 3. eliminating an apparentlylimitless variety of foreign invaders. cont… antigen ➢It is any foreign substance that when enters the body activates the immune response. antibody ➢ Is a protein produced by the B lymphocytes to attack and fight off antigens.
- 4. Fluid Systems ofthe Body • There are two main fluid systems: blood and lymph • They are intertwined throughout the body • Theyare responsible for transporting the agents of the immune system.
- 5. The Blood System •5 liters of blood of a 70 kg person constitute about 7% of the body's total weight • Composed of 52–62% liquid plasma and 38–48% cells • Three types of blood cells: 1) Erythrocytes (red blood cells or RBCs), 2) Leukocytes (white blood cells or WBCs), 3) Thrombocytes (platelets) Three types of blood cells:
- 7. Leukocytes • Further subdividedinto: ▪ Granulocytes (containing large granules in the cytoplasm) ▪ Agranulocytes (without granules) Granulocytes consist of: – Neutrophils (55–70%), – Eosinophils(1–3%), – Basophils (0.5–1.0%). Leukocytes…….
- 8. • Agranulocytes are: •Lymphocytes (20-40%) - Consisting of B cells and T cells • Monocytes (1-6%) • Lymphocytes circulate in the blood and lymph systems, and make their home in the lymphoid organs.
- 11. Erythrocytes • RBCs areproduced each second and each lives for about 120 days • RBCs antigens used in ABO blood grouping • Grouping is characterized by the presence or absence of A and/or B antigens on the surface of the RBCs. • Blood type AB means both antigens are present • Type O means both antigens are absent. • Type A blood has A antigens and type B blood has B antigens.
- 13. The Lymph System •Therearesmallbean-shaped lymph nodes that serve as filters of the lymphatic fluid. •It is in the lymph nodes where antigen is usually presented to the immune system. Understanding the lymphatic system • The lymphatic system consists of organs, ducts, and nodes. It transports a watery clear fluid called lymph
- 14. • Fluid distributesimmune cells and other factors throughout the body. It also interacts with the blood circulatory system to drain fluid from cells and tissues. • The lymphatic system contains immune cells called lymphocytes, which protect the body against antigens (viruses, bacteria, etc.) that invade the body Main functions of the lymphatic system • The lymphatic system aids the immune system in destroying pathogens and filtering waste so that the lymph can be safely returned to the circulatory system. • To remove excess fluid, waste, debris, dead blood cells, pathogens, cancer cells, and toxins from these cells and the tissue spaces between them.
- 15. • The lymphaticsystem also works with the circulatory system to deliver nutrients, oxygen, and hormones from the blood to the cells that make up the tissues of the body. Blood capillaries allow fluid to leave, and enter, the circulatory system
- 17. Lymph organs • Includethe bone marrow, lymph nodes, spleen, and thymus. Precursor cells in the bone marrow produce lymphocytes. B-lymphocytes (B-cells) mature in the bone marrow. T-lymphocytes (T-cells) mature in the thymus gland. • the ducts of the lymphatic system provide transportation for proteins, fats, and other substances in a medium called lymph. • "Means clear water and it is basically the fluid and protein that has been squeezed out of the blood (i.e. blood plasma).
- 18. The immune system 1.3.The immune system Immune System Innate (Nonspecific) Adaptive (Specific) Cellular Components Humoral Components Cell-Mediated Humoral (Ab)
- 19. Overview of theImmune System
- 20. The Innate immunity Naturalimmune system (Innate Immunity) ✓ Non – specific ✓ First line of defense ✓ Repeated exposure - no augmentation ◼ Components ✓Biochemical ✓Physical barrier ✓Cells 1. Components
- 21. a. Biochemical ◼ enzymes,C’, etc. ◼ secretions ◼ pH b. Physical ◼ skin ◼ Mucous membrane c. Cells ◼ Phagocytes, NK
- 22.
- 23. Lysozymes Mucus Sebaceous glands Skin Cilia: trachea Acidin stomach Commensal organisms in gut & vagina Spermine in semen
- 24. Innate immunity ◼ Itis divided into two parts 1st line of defence (External Innate Defense system) 2nd line of defence (Internal Innate Defense System)
- 25. 1. External InnateDefense Systems ◼ Skin Keratinzed dead layer, sweat and sebum, hair and normal flora ◼ Mucous membrane Mucus and cilia Gastric acid Vagina ph Urine ph Saliva and tears
- 27. cont… cont… ◼ Prevent entrance: Structural barriers – effective with most microorganisms ◼ Skin - epidermis = layers of tightly packed epithelial cells. Outer layer is dead cells and keratin, waterproofing protein ◼ Inner layer skin - dermis = blood vessels, hair follicles, sweat glands, and sebaceous glands that produce an oily secretion called sebum ◼ Cilia and cough reflex – helps expel microbe containing mucous ◼ Sneeze
- 28. cont… ◼ Mucus -conjunctivae, alimentary, respiratory, and urogenital tracts • saliva, tears, and mucous secretions wash away invaders and contain antibacterial or antiviral substances. • acidity (pH 5.6) of sweat, sebaceous glands, vagina (pH 5) and stomach (pH 1) – unfriendly to many microorganisms ◼ enzymes present in the skin and stomach, tears ◼ Normal flora - out compete pathogens for attachment sites on the epithelial cell surface and for necessary nutrients.
- 29. cont… 2. Internal InnateDefense System ◼ Cells Neutrophils, eosinophil, basophils and mast cells Dendritic cells and monocyte (macrophages) antigen presenting cells ◼ Physiology Inflammation fever ◼ Chemicals Interferon
- 30. cont… Complement proteinsand other chemicals produced by the cells ◼ To prevent expansion of penetration Recognize carbohydrates not normally present on cells such as mannose May cause nonspecific activation of white cells ◼ Phagocytosis – by neutrophils, eosinophils, basophils, or macrophages, mast cells, and dendritic cells Clotting mechanism which entraps organisms in fibrin clots Complement System can lyse cells or enhance phagocytosis
- 31. cont… Physiologic Barriers ◼ Solublefactors contribute to innate immunity, they are collectively known as acute phase reactants. ◼ Normal serum components, non-specific responders to inflammation ◼ Increase because of infection, injury, trauma ◼ Produced mostly by liver in response to inflammation and cytokine stimulation Cytokines: IL-1, IL-6 and TNF alpha which are produced by macrophages and monocytes at inflammatory site are activators
- 32. cont… ◼ Complement –a series of enzymes normally circulating in an inactive form May be activated by the classical or alternate pathways Can result in lysis or enhanced phagocytosis of cells ◼ Lysozyme, a hydrolytic enzyme in mucous secretions and in tears, can cleave the peptidoglycan layer of bacterial cell wall. ◼ Interferon, proteins produced by virus-infected cells. Has many functions including ability to bind to nearby cells and induce a generalized antiviral state. ◼ Phagocytosis Is a form of endocytosis.
- 33. cont… Important bodydefense mechanism is process in which specialized cells engulf and destroy foreign particles such as microorganisms or damaged cells. Macrophages and segmented Neutrophiils are the most important phagocytic cells. ◼ Can be divided in to several stages: chemotaxis – attraction of leukocytes or other cells by chemicals Movement of neutraphils is influenced by chemotaxins – chemical messangers
- 34. cont… ◼ Complement, proteinsfrom coagulation, ◼ Products from bacteria and viruses, ◼ Secretions from mast cells, lymphocytes, macrophages, and other neutrophils Phagocytosis ◼ Phagocytic cells Chemotaxins such as Complement components Coagulation cascade proteins Bacterial and viral products ◼ Attract phagocytic cells including: Mast cell, lymphocyte, macrophage, neutrophil products ◼ Physical contact between phagocytic cell and foreign object results in
- 35. cont… Formation ofphagosome Digestion Release of debris ◼ Phagocytosis ... Adherence – binding of organism to the surface of phagocytic cell. Engulfment:- is the ingestion and formation of phagosomes. Digestion – after the foreign particle is ingested, cytoplasm lysosome fuse with phagosome The
- 36. cont… enzymes of lysosomethen contribute to microbial killing and lysis. Phagocytosis ...
- 37. cont… Source: Kuby immunology2007, 5th ed
- 38. 1.5. The adaptiveimmune system The adaptive immune system Immune System Innate ) pecific Nons ( Adaptive (Specific) Cellular Components Humoral Components Cell-Mediated Humoral (Ab)
- 40. The adaptive immunesystem Adaptive Immunity ➢ Specific ➢ Second line of defense ➢ Repeated exposure - augmented – memory ➢ Faster response ➢ More vigorous response ➢ Longer lasting response Components Classic Immune System ➢ Cells (Cell mediated) =CMI ➢ Soluble Factors (Humoral immunity) = HI ◼ It is divided into two
- 41. Humoral ◼ Bcell – plasma cells (antibodies) and memory cells Cell mediated ◼ T cells T helper cells (CD4+) - activated cells and memory cells Cytotoxic T cells (CD8+) – activated cells and memory cells T regulatory cells The adaptive immune system ◼ Capable of recognizing and selectively eliminating specific foreign microorganisms and molecules(i.e., foreign antigens). ◼ Unlike innate immune responses, adaptive immune responses are reactions to specific antigenic challenges
- 42. ◼ Different populationsof lymphocytes and their products are the major actors together with accessory cells – Antigen presenting cells (APCs) ◼ Cardinal features are : Specificity Diversity , Memory, The adaptive immune system Cardinal Features of adaptive Immune Responses ◼ Specificity – specific for distinct antigen, and for different structural components of a single complex protein, polysaccharide, or other macromolecules.
- 43. Portions ofsuch antigens recognized by individual lymphocytes are called determinants or epitopes. This fine specificity exists because individual lymphocyte express membrane receptors able to distinguish subtle (slight) differences in structure between distinct antigens. The adaptive immune system ◼ Diversity- total number of antigenic specificities of the lymphocytes in an individual, called the lymphocyte repertoire, is extremely large. estimated mammalian immune system can discriminate 109 to 1011 distinct antigenic date ruminants.
- 44. This propertyof the lymphocyte repertoire is called diversity. It is the result of variability in the structures of antigen- binding sites of lymphocyte receptors for antigens. The adaptive immune system ◼ Memory- Exposure of the immune system to foreign antigen: enhances its ability to respond again to that antigen.
- 45. Responses tosecond and subsequent exposure to the same antigen, called secondary immune responses, are usually more rapid and larger than the first or primary immune response. The adaptive immune system ◼ An effective immune response involves three major groups of cells: Cellular Immunity (T lymphocytes), Humoral Immunity (B cells), and Accessory cells (antigen-presenting cells).
- 46. ◼ The twomajor populations of lymphocytes—B lymphocytes (B cells) of Humoral immunity and T lymphocytes (T cells) of Cellular Immunity provide us with our specific adaptive immunity The adaptive immune system ◼ Specialization –the immune system responds in distinct and special ways to different microbes, maximizing the efficiency of antimicrobial defense mechanisms. Thus, humoral immunity and cell mediated
- 47. immunity are elicitedby different classes of microbes or by the same microbe at different stages of infection (extra cellular & intra cellular) ◼ Self –limitation- All normal immune responses returning the immune system to its resting or basal state with time after antigen stimulations, process called homeostasis.
- 49. Humoral defense • Involvesproduction of antibodies. • Initial exposure to an antigen results in the production of low affinity antibodies •Continued exposure to antigen leads to the production of high affinity antibodies. • In primary antibody response, B cells are activated to produce IgM antibody • By 3-5 days, specific antibodies mainly of the IgM appear in serum and concentration increases until a pick is reached in 10-14 days • Antibody titre then fall to pre-immunization level after some weeks
- 50. Humoral defense • Uponimmunization, there is more rapid and extensive development of antibody producing cells in regional lymph nodes and many of them undergo isotope switch to produce IgG or other immunoglobulin classes of specific antibodies. • Antibodies function to inactivate viruses or bacteria toxins by blocking their binding sites and label microorganisms for destruction by phagocytes or complement- mediated lysis.
- 54. Summary of innateand adaptive immunity Comparison of Innate and Adaptive Immunity Innate Immunity Adaptive Immunity • No time lag • Not antigen specific • No memory • A lag period • Antigen specific • Development of memory
- 55. Tissue Transplant ◼ Histocompatibility:Matching of donor and recipient tissue to minimize rejection. Major Histocompatibility Complex (MHC) plays a crucial role. ◼ Compatibility of RH and ABO blood group ◼ Rejection: Host immune system recognizes the transplanted tissue as foreign and mounts an immune response.
- 56. Hypersensitivity Reaction ◼ Hypersensitivityreactions are exaggerated or inappropriate immune responses to antigens (foreign substances) that can lead to tissue damage. There are four types of hypersensitivity reactions: Hypersensitivity reaction ◼ Type I (Immediate Hypersensitivity): Rapid onset (within minutes) Mediated by IgE antibodies
- 57. Examples: Allergicreactions (e.g., hay fever, asthma, anaphylaxis) ◼ Type II (Cytotoxic Hypersensitivity): Mediated by IgG or IgM antibodies Antibodies target antigens on host cells, leading to cell destruction by complement activation or phagocytosis Examples: Blood transfusion reactions, autoimmune hemolytic anemia Hypersensitivity reaction ◼ Type III (Immune Complex-Mediated Hypersensitivity):
- 58. Mediated byimmune complexes (antigen-antibody complexes) depositing in tissues and causing inflammation and tissue damage Examples: Systemic lupus erythematosus (SLE), rheumatoid arthritis ◼ Type IV (Delayed-Type Hypersensitivity): Delayed onset (hours to days) Mediated by T cells (specifically, CD4+ T cells or CD8+ T cells) Results in inflammation and tissue damage Examples: Contact dermatitis (e.g., poison ivy), Tuberculin skin test reaction Auto Immune Diseases ◼ Autoimmune diseases occur when the immune system fails to distinguish between self and nonself
- 59. antigens, leading toan attack on the body's own tissues. ◼ The exact cause of autoimmune diseases is not fully understood, but factors such as genetics, environmental triggers, and infections play a role. Auto Immune Diseases ◼ Autoantibodies: Antibodies mistakenly produced by the immune system that target selfantigens, leading to tissue damage.
- 60. ◼ T CellDysfunction: Dysregulation of T cells, including CD4+ T helper cells and CD8+ cytotoxic T cells, which play a central role in orchestrating immune responses. ◼ Examples: inflammatory bowel diseases, diabetes type 1 etc.
- 61. Summary of innateand adaptive immunity Infectious Exposure Innate Immunity holds Innate Immunity Fails Disease Adaptive Immune system Recovery Second Infectious Exposure Same organism Adaptive Immunity Specific memory No Disease
- 62. Adaptive and Innate- Interactions