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Transcript
Lecture 13 – Ch. 43: Immune System I. II. Overview Innate Immunity A. components B. cells IIII. Adaptive/acquired immunity A. Lymphocytes i. B-cells ii. T-cells B. humoral vs. cell-mediated immunity C. Antibodies D. MHC molecules IV. Immune memory V. Immune System Problems VI. Preparation for next lecture Thought Question: Why do we not get sick EVERY time someone near us sneezes? Overview cilia of tracheal cells Pathogens Viruses Bacteria Macroparasites Irritants Pollen Dust dust For example… Virus Bacteria Macroparasites Influenza Strep Malaria Ebola Black Plague Sleeping Sickness Chicken Pox Salmonella River Blindness West Nile Virus E. Coli Elephantiasis pollen Overview A Way In? Skin breeches (cuts, punctures, scrapes) Mucus membranes Eyes Nose Mouth Vagina Urethra Antigens = foreign molecules specific to the invader Immunity Overview Pathogens (bacteria, fungi, and viruses) INNATE IMMUNITY (all animals) • Recognition of traits shared by broad ranges of pathogens, using a small set of receptors • Rapid response ADAPTIVE IMMUNITY (vertebrates only) • Recognition of traits specific to particular pathogens, using a vast array of receptors • Slower response Barrier defenses: Skin Mucous membranes Secretions Internal defenses: Phagocytic cells Natural killer cells Antimicrobial proteins Inflammatory response Humoral response: Antibodies in body fluids Cell-mediated response: Cytotoxic cells disrupt pathogens. Innate Immunity External Barriers Skin Dry dead cells Constantly sloughed off Secretions Contain natural antibiotics Mucus physically traps microbes Internal Barriers Phagocytic cells – detect and engulf pathogens Mast cells – cause inflammation and alert of damaged tissues Innate Immunity Leukocytes Phagocytes - ingest foreign particles & cellular debris Macrophages – consume many cells Neutrophils – die upon consumption Dendritic cells – stimulate adaptive immunity Eosinophils – helpful against parasites, destructive enzymes Dendritic cell Natural killer cells Attack cancerous or infected body cells Use proteins & enzymes to lyse cells Inflammation Innate Immunity Initiated by damaged or infected cells Histamine release by mast cells Capillary flow and permeability increased Phagocytes drawn to area Cytokines – recruit more lymphocytes leads to pus, swelling, redness, heat Innate Immunity Inflammatory “Symptoms” Warm, red, painful Result of leaky capillaries Increased fluid secretions Removal of dead cells and waste Pain Swelling, chemical response Alerts injured organism Leukocytes and fluid = pus NSAIDs Innate Immunity Antimicrobial peptides first discovered in insects (like Drosophila). Here, AMPs engineered to glow green; upper fly infected by bacteria. Antimicrobial peptides in vertebrates: the complement – family of proteins, activated by infection and lyse infected cells Interferons – chemicals made by infected cells, trigger anti-viral response Adaptive Immune System Acquired/ adaptive immunity – lymphocytes made in bone marrow B cells and T cells Antigen receptors mature in bone marrow mature in thymus Antibodies; secreted or embedded in B cell membrane Cozy up to infected Mature B cell cells, bind, sometimes lyse Mature T cell Responsible for circulating antibodies, remembering pathogens, destroying infected cells Adaptive Immune System B cells Humoral immunity B cells & antibodies attack pathogens before they enter cells After encounter pathogen, B cells differentiate into memory B cells and antibody-producing cells Each B cell produces unique antibodies Over 100 million different antibodies in body chances of an antigen encountering one that fits are high Antigen receptor Antibody B cell Antigen Epitope Pathogen (a) B cell antigen receptors and antibodies Antibody C Antibody A Antibody B Antigen (b) Antigen receptor specificity Adaptive Immune System Antibody action Defend against pathogens in blood or fluid Can inactivate pathogens by binding to epitopes Can stimulate phagocytosis Can neutralize toxins or block adhesion Can trigger complement system where blood proteins destroy invaders Adaptive Immune System T cells Cell-mediated immunity T cell receptors – recognize pathogen pieces ‘presented’ on infected cells Displayed antigen fragment T cell T cell antigen receptor MHC molecule Antigen fragment Pathogen Host cell Cytotoxic T cells: Insert pores in infected cells, enzymes break down cells Helper T cells: stimulate B & cytotoxic T cell division Some T cells develop into memory cells Adaptive Immune System Self-tolerance MHC = major histocompatibility complex All cells have MHC molecules – most body cells have MHC I (lymphocytes have MHC II in addition) MHC molecules displayed on cell surface – each binds a specific peptide foreign fragment then “displays” it on surface. Adaptive Immune System Self-tolerance T-cells (cytotoxic or helper T) bind to MHC presented antigens Self-reactive lymphocytes with receptors to self epitopes are eliminated before they leave bone marrow and mature Adaptive Immune System Humoral (antibody-mediated) immunity Cell-mediated immunity Key Antigen (1st exposure) Engulfed by Antigenpresenting cell Stimulates Gives rise to B cell Helper T cell Cytotoxic T cell Memory helper T cells Antigen (2nd exposure) Plasma cells Memory B cells Memory cytotoxic T cells Active cytotoxic T cells Secreted antibodies Defend against extracellular pathogens Defend against intracellular pathogens and cancer Adaptive Immune System Immune system must remember past victories... • Memory cells “remember” specific antigens • May survive for years • Respond faster and larger to repeat invasion Adaptive Immune System Memory Memory B and T cells are able to recognize pathogens and fight off infections immediately Then why do you keep catching a cold every year? 100+ rhinoviruses Cold viruses can mutate quickly Vaccinations take advantage of the immune response Body is exposed to antigens to stimulate memory cells Antibiotics Antibiotics aid disease fight Reduce growth and reproduction of living pathogens (not viruses) Give immune system time to fight infection Humans have misused antibiotics “superbugs” Overuse of antibacterial products Failure to complete full course of antibiotics Non-medicinal use of antibiotics Immune System Problems Allergies Immune overreaction to harmless antigens Histamine triggers inflammation Extreme response can trigger anaphylaxis Autoimmune Disorders Immune system attacks healthy body cells Lupus, Rheumatoid Arthritis, Multiple Sclerosis, Type 1 Diabetes, Celiac disease, Crohn’s disease Immune System Problems Immune rejection When tissue with “non-self” MHC molecules contact immune system, response mounted Can be countered by immunosuppressive drugs Immune Deficiency Syndromes Severe Combined Immune Deficiency (SCID): Few/no immune cells produced genetic Acquired Immune Deficiency Syndrome (AIDS): Due to Human Immunodeficiency Virus (HIV) Destroys helper T cells Thought Question: What can you do to fortify your immune system? Things To Do After Lecture 13… Reading and Preparation: 1. Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms. 2. Ch. 43 Self-Quiz: #1 – 7 (correct answers in back of book) 3. Read chapter 43, focus on material covered in lecture (terms, concepts, and figures!) 4. Skim next lecture. “HOMEWORK” (NOT COLLECTED – but things to think about for studying): 1. Compare and contrast: T cells and B cells, the humoral response compared to the cell-mediated immune response. 2. Explain the function and parts of the human innate immune system. 3. Describe the problem with each of the following: allergies, autoimmune disorders, immune deficiency syndromes. 4. Why are people concerned about over-use or misuse of antibiotics?