Chapter 17 Immunity East Valley Institute of Technology What is the immune system? • Made up of primarily blood cells and the lymphatic system What is the lymphatic system? 2 important functions Process of immunity Maintaining fluid balance in the body Lymph: watery substance formed from fluid that filters into body tissues (except brain and placenta) or interstitially Lymphatic tissue consists of the tonsils, thymus, spleen, nodes, and vessels. But what does the lymphatic system DO? • Lymph is pushed into lymphatic vessels • Vessels carry lymph to lymphatic organs • Lymphatic organs filter out pathogens, debris, foreign materials, etc. • Lymph is returned to circulation via lymphatic vessels • Stuff that has been filtered out with be taken care of via: • Destruction • Excretion Infection • Reaction caused by microorganisms within the body Requires 3 elements Source of microorganisms Susceptible host Means of transmission to the host Why do infections occur? The Chain of Infection • Pathogen - Virulence and dose of the organism is a factor • Reservoir - Place for the pathogen to multiply • Place of Exit - How the pathogen leaves the reservoir • Method of transmission - How the pathogen travels to a new host • Portal of Entry - How the pathogen enters the host • Susceptible host - Predisposition to infection is a factor The Immune System • 2 Types of Defenses against disease • Nonspecific: effective against anything harmful • Specific: effective against a certain agent only Nonspecific Defenses • 1st line of defense • Chemical and mechanical barriers • Ex: skin, mucous membranes, cilia, tears, sneezing, coughing, vomiting, diarrhea Nonspecific Defenses • 2nd line of defense • Phagocytosis • NK Cells • Inflammation (cytokines) • Fever • Interferon • Complement Phagocytosis: WBC takes in and destroys waste and foreign material • Performed by macrophages and neutrophils Natural Killer Cells (NK cells): Type of lymphocyte that recognizes body cells with abnormal membranes • Found in lymph nodes, spleen, bone marrow, and blood • Secrete protein that breaks down cell membrane Interferons: Group of substances that prevent nearby cells from producing more of a virus • Also acts nonspecifically on immune system cells and can help to suppress autoimmune responses Complement: Group of nonspecific proteins that cause destruction of foreign cells • Always present in blood but must be activated by contact with foreign cell surfaces or complexes Complement: • Works by: • Coating foreign cell to attract phagocytes • Destroys cells by forming complexes that punch holes in membranes Complement: • Works by (continued): • Promote inflammation • Attract phagocytes Inflammation: reaction to infection caused by pathogens • Leads to: • Redness, pain, heat, and swelling • Leukocytes enter tissue • Pus is produced • Enlargement of lymph nodes Fever: phagocytes release substances while they work that increase body temperature • This increase in temperature: • Stimulates phagocytes • Increases metabolism • Decreases some organisms’ ability to multiply Immunity • The power to overcome a specific agent of disease • 2 types • Innate (Inborn) immunity: inherited in genes • Acquired (Adaptive) immunity: develops after exposure to pathogen either naturally or artificially and can be both an active or passive process Naturally Acquired Immunity • Acquired through contact with specific disease organism • Active or passive Artificially Acquired Immunity Vaccination (immunization) can cause a person’s immune system to manufacture antibodies Preventative measure Risk of side effects Immune Responses 1. Foreign substance enters body 2. T cells recognize foreign antigens 3. Macrophages eat foreign antigens and work with Helper T cells to stimulate more lymphocyte and monocyte production 4. B cells are exposed to foreign antigens and stimulate plasma cell production Immune Responses • A foreign substance (antigen) must enter the body first THEN: • Induce immune response of certain lymphocytes • T cells (thymus) • B cells (Bursa of Fabricius) T Cells • Originate in stem cells in bone marrow, but mature in the thymus • Become sensitized to specific antigens and produce cell-mediated immunity • Types of T cells: • Cytotoxic (Killer) T cells: • Helper T cells: • Regulatory T cells: • Memory T cells: • Types of T cells: • Cytotoxic (Killer) T cells: destroy foreign cells • Helper T cells: stimulate other lymphocytes and macrophages to help destroy foreign cells • Regulatory T cells: help keep immune system from being overactive (destroy active T cells) • Memory T cells: stay in body and remember antigens; trigger rapid response if antigen appears again (VACCINES) Macrophages • Encounter and eat foreign antigens and work with Helper T cells to stimulate more lymphocyte and monocyte production. Macrophages • Ingest foreign antigen • Places marker protein of the antigen on itself • Meets up with Helper T cell that recognizes antigen marker • Causes Helper T cell to stimulate more WBCs B Cells • Going to be exposed to foreign antigens and stimulate plasma cell production • Recognize specific foreign antigens • Stimulate production of plasma cells and B memory cells B Cells • Plasma cells produce antibodies that will attach to the foreign antigens • Memory cells stay in blood and can produce antibodies upon repeated contact foreign antigens Disorders of the Lymphatic and Immune Systems • Allergy: tendency to react unfavorably to substances that are normally harmless; an antigen-antibody reaction takes place to cause the symptoms of an allergy Disorders of the Lymphatic and Immune Systems • Anaphylaxis: severe allergic response that occurs within seconds of exposure to the allergen; breathing problems, swollen throat and tongue, hives and shock are common Disorders of the Lymphatic and Immune Systems • Autoimmune: conditions in which the immune system reacts to body’s own antigens and turns against itself • Splenomegaly: an enlargement of the spleen caused by an acute infection such as scarlet fever, typhoid fever, or syphilis Disorders of the Lymphatic and Immune Systems Acquired Immunodeficiency Syndrome (AIDS): dysfunction of the immune system caused by the HIV; virus destroys Helper T Cells and causes individuals to be susceptible to disease easily Disorders of the Lymphatic and Immune Systems • Elephantiasis: massive accumulation of lymphatic fluid in lower body tissues resulting from lymphatic vessel blockage from filarial worms Disorders of the Lymphatic and Immune Systems • Hodgkin’s disease/lymphoma: chronic malignant cancer of the lymph nodes of unknown cause; 2 common age groups (early 20s for both sexes and again after 50 more in men)
