Chapter 43: The Immune System

1. Chapter 43: The Immune System Disease A departure from health Types: Deficiency diseases Genetic diseases Communicable diseases Contagious disease Infectious disease Host provides metabolic needs of pathogen or parasite

2. Infectious disease • Transmission • Contact • Droplet infection • Vector • Common vehicle transmission • Types • Sporadic disease • Endemic disease • Epidemic disease • Pandemic disease

3. Adaptations of pathogen to resist host defense • Cell wall • Contain proteins to resist host &/or antibiotics • Sticky capsule • Counters phagocytosis; increases virulence of pathogen • Production of enzymes or metabolic toxins • Manipulates host cell’s metabolic structure • viruses

4. Adaptations of the Human Body • 1st line of defense • Physical shield • Skin, mucus, ciliated cells, tears, urine flow, coughing, sneezing, ear wax • Chemical shield • Stomach acids kill bateria • Enzymes (lysozyme) in tears etc. • Skin acids • 2nd line: inflammatory response • Increased blood flow • Promotes healing • Swelling insulates tissues

7. Macrophages, neutrophils, Eosinophils, & Dendritic cells • Phagocytic activity to engulf pathogen • Macrophages: • Develop from monocytes • Migrate through the body or reside permanently in some organs (i.e. spleen) • Neutrophils: • Enter infected tissue to engulf microbes • Self destruct • Eosinophils: • Position against multi-cellular parasite & release enzymes to destroy • Dendritic cells: • Can act like macrophages but are usually involved in acquired immunity

8. Injured, circulating basophils release histamines & prostaglandins • Promotes vasodilation • Capillaries become “leaky” • Attracts phagocytic cells • Neutrophil engulfs bacteria macrophage engulfs neutrophil • Infected cells release interferon • Stimulate adjacent cells to produce proteins that prevent viral replication • Activates phagocytes

10. 3rd line: Immune response • Production of Lymphocytes • Circulate in blood & lymph • Concentrated in spleen, lymph nodes, & lymphoid tissue • Each lymphocyte is specific to a particular foreign antigen • Originate in stem cells of bone marrow • Types: • B cells • Mature in bone marrow • T cells • Mature in thymus gland • Maturing B cells & T cells tested for self-reactivity & destroyed if self reactive

12. Production of specific antibodies by lymphocytes • Antitoxins • Neutralize bacterial toxins • Agglutinins • Clumping of bacteria • Opsonins • Stimulate phagocytosis of clumped bacteria • Lysins • Dissolve cell walls of bacteria • Precipitins • Coagulation chemicals of bacteria

13. Immunoglobins (antibodies) • Specific antigen binding immunoglobulins • Generated by B cells • Types • IgM • First antibodies to arrive at infection site • IgC • Most abundant antibodies in blood & lymph • IgA • Antibodies found in body secretions (saliva, sweat) • IgE • Trigger release of histamines & other chemicals by mast cells & basophils to cause allergic reactions • IgD • On naïve B cells (not yet exposed to foreign antigen) • Receives antigen that leads to clonal selection

16. Self/non-self • Immune system must be able to distinguish foreign from non-foreign proteins • Major histocompatability complex (MHC) • Group of glycoproteins embedded in cell membrane • Two major classes of MHC • Class I MHC • Bind to cytotoxic T cells • Class II MHC • Known as antigen presenting cells • Bind to specialized cells (macrophages, B cells) & activate T cells

18. Action of lymphocytes • Humoral Response • B cells • Enter blood & produce specific antibodies to counter specific antigens • Antigen-antibody complexes are formed • Helper T cells • Secrete interleukins • Stimulate clonin of B cells to memory cells • B cells into memory cells (M cells) • Long lived cells • Recognize specific antigen • Basis of active immunity • Plasma cells (P cells) • Short lived cells • Produce additional antibodies with initial exposure to antigen • Antibodies draw phagocytic cells in to destroy

23. Cell mediated response • Cytotoxic T cells • Stored in thymus gland prior to moving into blood • Activated when CD8 receptors recognize antigen on Class I MHC; helper T cell releases cytokines to promote activation • Do not produce antibodies • Attack & kill antigen-bearing cells • Secrete proteins that destroy infected cells • Stimulate the production of B cells • Dispose of infected cells • Suppress B cell reproduction when infection has been suppressed • Secrete interferon which defends healthy cells from virus

26. Primary vs. Secondary immune response • Primary immune response • First exposure or vaccination to antigen • Results in formation a specific antibody to inactivate an antigen • Requires time to occur • Secondary immune response • Rapid reproduction of specific antibodies to inactivate & destroy antigen (immediate)

27. Types of Defense • Innate immunity • Present at birth without any exposure • Non-specific • Acquired immunity/adaptive immunity • Develops after exposure • Highly specific • Recognition by lymphocytes

28. Types of immunity • Natural immunity • Inherited immunity (parent to child) • Active immunity • Long term immunity due to • Exposure (i.e. chicken pox, mumps, measles) • Vaccination • Intentional exposure to weakened/dead pathogen or pathogenic toxin • Immunization • Polio...

29. Passive immunity • Borrowed or temporary immunity through • Injection of antibodies • Blood serum or gamma globulin injections • Immediate immunity • Short term immunity • Memory cells are not produced

30. Blood Groups effect on transfusions & transplants • Antibodies present against non-self blood types without exposure • result of reaction to bacterial antigens • MHC molecules stimulate immune response leading to tissue rejection • each person has a unique polymorphic combination of MHC molecules

31. Exaggerated, self-directed or diminished immune response & disease • Allergies • Hypersensitive response to antigens on allergens • Often involve IgE antibodies • Attach to mast cells to induce histamine release • Anaphylactic shock • Whole body, life threatening allergic reaction • Autoimmune disease • Body generates antibodies against self • Ex. Lupus, rheumatoid arthritis, multiple sclerosis, diabetes mellitus

33. Immunodeficiency diseases • Inborn or primary • Caused by genetic or developmental defect • Defect in production of immune cells or specific proteins • Acquired or secondary • Develops later in life • Caused by exposure to agents or disease • Ex. Hodgkin's, AIDS