CAMPBELL BIOLOGY IN FOCUS Urry Cain Wasserman Minorsky
CAMPBELL BIOLOGY IN FOCUS Urry • Cain • Wasserman • Minorsky • Jackson • Reece 35 The Immune System Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge © 2014 Pearson Education, Inc.
Do now: § What are pathogens? Provide 2 examples each of diseases that are caused by pathogens and 2 that are not. § Do all organisms have immune systems? Explain. § What is microbiodata? Provide locations where one might find them. © 2014 Pearson Education, Inc.
Some types of pathogens (there are others) © 2014 Pearson Education, Inc.
Most multicelluar organisms have immune systems. Pathogens (such as bacteria, The type and complexity varies from fungi, and viruses) one organisms to another 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 © 2014 Pearson Education, Inc. Barrier defenses: Skin Mucous membranes Secretions Internal defenses: Phagocytic cells Natural killer cells Antimicrobial proteins Inflammatory response Humoral response: Antibodies defend against infection in body fluids. Cell-mediated response: Cytotoxic cells defend against infection in body cells.
http: //www. scientificamerican. com/article/microbi ome-graphic-explore-human-microbiome/ © 2014 Pearson Education, Inc.
Innate = non specific response § Innate immunity is present before any exposure to pathogens and is effective from the time of birth § It involves nonspecific responses to pathogens § Innate immunity consists of § external barriers § Example? (wkbk page 171/174) § internal cellular and chemical defenses § Example? (wkbk page 171/174) © 2014 Pearson Education, Inc.
Concept 35. 1: In innate immunity, recognition and response rely on traits common to groups of pathogens § Innate immunity is found in all animals and plants § In vertebrates, innate immunity is a first response to infections and serves as the foundation of adaptive immunity © 2014 Pearson Education, Inc.
Plant Defenses: Identify either as active or passive and explain why you categorize it this way and how this immunity protects the plant (WKBK page 170) §A B §C © 2014 Pearson Education, Inc. D
Animals: Innate Immunity of Invertebrates (Wk page 169) § Insects § Exoskeleton § barrier § Lysozyme § Break down bacterial cell walls § Hemocytes § Release antimicrobial peptides which break down cell (plasma) membranes of bacteria and fungi § Why is breaking down cell wall/cell membrane an effective strategy? © 2014 Pearson Education, Inc.
Animals: Innate Immunity of Vertebrates (focus on mammals) **know these well § Innate defenses § barrier defenses § phagocytosis** § antimicrobial peptides § Additional defenses are unique to vertebrates: § natural killer cells § interferons, § inflammatory response** © 2014 Pearson Education, Inc.
Barrier Defenses: Skin and mucous membrane § Why might the following areas need a mucous membrane? § Respiratory § Urinary/Excretory § reproductive § Many body fluids including saliva, mucus, and tears are hostile to many microbes § Why is creating an environment of low p. H and effective strategy for barrier protection? © 2014 Pearson Education, Inc.
Identify this process and explain what is occurring at each arrow (WKBK page 176) © 2014 Pearson Education, Inc.
Figure 35. 3 Pathogen 1 Pseudopodia surround pathogens. PHAGOCYTIC CELL 2 Pathogens engulfed by endocytosis. 3 Vacuole forms. Vacuole Lysosome containing enzymes 4 Vacuole and lysosome fuse. 5 Pathogens destroyed. 6 Debris from pathogens released. © 2014 Pearson Education, Inc.
Evasion of Innate Immunity by Pathogens (wkbk: page 176) • Phagocytes are killed • Microbes are evaded – Tuberculosis (TB) resists breakdown within lysosomes after being engulfed by a host cell • Dormant microbes hide inside © 2014 Pearson Education, Inc.
Phagocytosis § There are two main types of phagocytic cells in mammals § Neutrophils circulate in the blood and are attracted by signals from infected tissues § Macrophages are found throughout the body § Two additional types of phagocytic cells § Dendritic cells stimulate development of adaptive immunity in cells that contact the environment (such as skin) § Eosinophils discharge destructive enzymes beneath mucosal surfaces © 2014 Pearson Education, Inc.
© 2014 Pearson Education, Inc.
Natural Killer Cells § These circulate through the body and detect abnormal cells § They release chemicals leading to cell death, inhibiting the spread of virally infected or cancerous cells § Many cellular innate defenses involve the lymphatic system © 2014 Pearson Education, Inc.
Inflammatory Response: defensive mechanism to damage of skin WK 177 Pathogen Splinter • Identify the first step of the response. Mast cell Signaling molecules Macrophage Capillary Red blood cells Neutrophil 1 Histamines and cytokines released. Capillaries dilate. © 2014 Pearson Education, Inc.
Figure 35. 5 -2 Pathogen Splinter • Movement of fluid – Mast cell Signaling molecules Macrophage Capillary Red blood cells Neutrophil 1 Histamines and cytokines released. Capillaries dilate. © 2014 Pearson Education, Inc. 2 Antimicrobial peptides enter tissue. Neutrophils are recruited. Identify 2 nd Step
Figure 35. 5 -3 Pathogen Splinter Movement of fluid Mast cell Signaling molecules Macrophage Capillary Red blood cells Neutrophil 1 Histamines and cytokines released. Capillaries dilate. © 2014 Pearson Education, Inc. Phagocytosis 2 Antimicrobial peptides enter tissue. Neutrophils are recruited. 3 Neutrophils digest pathogens and cell debris. Tissue heals.
Inflammatory Response § The inflammatory response, such as pain and swelling, is brought about by molecules released upon injury of infection § Mast cells release histamine, which triggers blood vessels to dilate and become more permeable § Activated macrophages and neutrophils release cytokines, signaling molecules that modulate the immune response and promote blood flow to the site of injury or infection © 2014 Pearson Education, Inc.
§ Enhanced blood flow to the site helps deliver antimicrobial peptides § This results in an accumulation of pus, a fluid rich in white blood cells, dead pathogens, and cell debris from damaged tissues Video: Leukocyte Rolling Video: Neutrophil Chemotaxis © 2014 Pearson Education, Inc.
§ Inflammation can be either local or systemic (throughout the body) § Fever is a systemic inflammatory response triggered by substances released by macrophages § Septic shock is a life-threatening condition caused by an overwhelming inflammatory response § Chronic inflammation can also threaten human health © 2014 Pearson Education, Inc.
Lesson #1 EXIT TICKET: §Explain the role phagocytosis, inflammation and microbiodata play in the innate immunity of the human body © 2014 Pearson Education, Inc.
Lesson #2: Adaptive Immunity Do now: • Fill in the blanks • Identify A. • Categorize the cell as belonging to either cell mediated or humoral response • Describe the main function of each response © 2014 Pearson Education, Inc. ? ? ? A Mature __ cell bone marrow Mature __ cell thymus
Antigen receptors on B cells vs T cells Similarities? Differences? B cells © 2014 Pearson Education, Inc. T cells
Antigen Recognition by B Cells and Antibodies § Each B cell antigen receptor is a Y-shaped molecule with two identical heavy chains and two identical light chains § The constant (C) regions of the chains vary little among B cells, whereas the variable (V) regions differ greatly § Together, the V regions of the heavy and light chains form an antigen-binding site © 2014 Pearson Education, Inc.
Antigen Recognition by T Cells § Each T cell receptor consists of two different polypeptide chains (called and ) § The tips of the chain form a variable (V) region; the rest is a constant (C) region § The V regions of the and chains together form an antigen-binding site © 2014 Pearson Education, Inc.
§ Recognition occurs when a B or T cell binds to an antigen, via an antigen receptor § What are antigens? § The immune system produces millions of different antigen receptors. § Are the antigen receptors the same on each cell? § How is it possible to create so many types? © 2014 Pearson Education, Inc.
Figure 35. 9 Displayed antigen fragment ? ? cell D C B A Host cell © 2014 Pearson Education, Inc.
Figure 35. 9 Displayed antigen fragment T cell antigen receptor MHC molecule Antigen fragment Pathogen Host cell © 2014 Pearson Education, Inc.
Concept Quick Check Identify as true or false: 1) The macrophage engulfs the T cell 2) The macrophage displays the antigen on its surface 3) The T cell interacts directly with the live pathogen 4) The B cell gets activated once it is in contact with the APC © 2014 Pearson Education, Inc.
Figure 35. 13 Antigenpresenting cell Antigen fragment Pathogen Class II MHC molecule Accessory protein (CD 4) Antigen receptor 1 Helper T cell Cytokines 2 B cell Humoral immunity © 2014 Pearson Education, Inc. 3 3 Cytotoxic T cell Cell-mediated immunity
Helper T Cells: A Response to Nearly All Antigens 1) A type of T cell called a helper T cell triggers both the humoral and cell-mediated immune responses 1)An antigen must be displayed on the surface of an antigen-presenting cell and bind specifically to the antigen receptor of a T cell § Antigen-presenting cells have class I and class II MHC molecules on their surfaces § MHC is involved in transplants… (TBC in lesson #3) © 2014 Pearson Education, Inc.
§ 2) The helper T cell is activated, proliferates, and forms a clone of helper T cells § 3)which then activate the appropriate B cells Animation: Helper T Cells Video: Cell Receptors © 2014 Pearson Education, Inc.
Proliferation of B Cells and T Cells § If there are T cells and B cells with thousands of different receptors, how do we make sure to replicate the right one? § In the lymph nodes, an antigen is exposed to a steady stream of lymphocytes until a match is made § This binding of a mature lymphocyte to an antigen initiates events that activate the lymphocyte § Evolutionarily speaking: why do you think this strategy exists? © 2014 Pearson Education, Inc.
Figure 35. 11 B cells that differ in antigen specificity Antigen receptor ? ? ? cells © 2014 Pearson Education, Inc. ? ? ? cells
Figure 35. 11 B cells that differ in antigen specificity Antigen receptor Antibody Memory cells © 2014 Pearson Education, Inc. Plasma cells
Clonal Selection Theory (wkbk page 184) § What is it? § Once activated, a B or T cell undergoes multiple cell divisions to produce a clone of identical cells (called clonal selection) Animation: Role of B Cells © 2014 Pearson Education, Inc.
How Antibodies inactivate Antigens (wkbk pg 185) § Secreted antibodies are similar to B cell receptors but are not membrane bound § How do antibodies disable pathogens? § Neutralization § Agglutination § Precipitation § Activation of complement Animation: Antibodies © 2014 Pearson Education, Inc.
Concept 35. 3: Adaptive immunity defends against infection of body fluids and body cells § B and T lymphocytes produce a humoral immune response and a cell-mediated immune response § In the humoral immune response, antibodies help neutralize or eliminate toxins and pathogens in the blood and lymph § In the cell-mediated immune response specialized T cells destroy infected host cells © 2014 Pearson Education, Inc.
Cytotoxic T Cells: A Response to Infected Cells § Cytotoxic T cells are the effector cells in the cellmediated immune response § Cytotoxic T cells recognize fragments of foreign proteins produced by infected cells and possess an accessory protein that binds to class I MHC molecules § The activated cytotoxic T cell secretes proteins that disrupt the membranes of target cells and trigger apoptosis Animation: Cytotoxic T Cells © 2014 Pearson Education, Inc.
Figure 35. 14 -1 Cytotoxic T cell Accessory protein Class I MHC molecule Infected cell 1 © 2014 Pearson Education, Inc. Antigen receptor Antigen fragment
Figure 35. 14 -2 Cytotoxic T cell Accessory protein Class I MHC molecule Infected cell 1 © 2014 Pearson Education, Inc. Perforin Antigen receptor Pore Antigen fragment 2 Granzymes
Figure 35. 14 -3 Cytotoxic T cell Accessory protein Class I MHC molecule Infected cell 1 © 2014 Pearson Education, Inc. Perforin Released cytotoxic T cell Granzymes Antigen receptor Dying infected cell Pore Antigen fragment 2 3
B Cells and Antibodies: A Response to Extracellular Pathogens § The humoral response is characterized by secretion of antibodies by clonally selected B cells § Activation of B cells involves helper T cells and proteins on the surface of pathogens § In response to cytokines from helper T cells and an antigen, a B cell proliferates and differentiates into memory B cells and antibody-secreting effector cells called plasma cells © 2014 Pearson Education, Inc.
Figure 35. 15 -1 Pathogen Antigenpresenting cell Antigen fragments MHC CD 4 Antigen receptor 1 Helper T cell © 2014 Pearson Education, Inc.
Figure 35. 15 -2 Pathogen Antigenpresenting cell B cell Antigen fragments MHC CD 4 Cytokines Antigen receptor 1 Helper T cell © 2014 Pearson Education, Inc. 2 Activated helper T cell
Pathogen Antigenpresenting cell B cell Memory B cells Antigen fragments MHC CD 4 Cytokines Antigen receptor Helper T cell © 2014 Pearson Education, Inc. Activated helper T cell Plasma cells Secreted antibodies
Figure 35. 16 Humoral (antibody-mediated) immune response Cell-mediated immune response Antigen (1 st exposure) Key Engulfed by Stimulates Gives rise to Antigenpresenting cell B cell Cytotoxic T cell Helper T cell Memory helper T cell Antigen (2 nd exposure) Plasma cells Secreted antibodies © 2014 Pearson Education, Inc. Memory B cells Defend against extracellular pathogens Memory cytotoxic T cells Defend against intracellular pathogens and cancer Active cytotoxic T cells
Exit Ticket • Explain the steps that would take place after a helper T cell recognizes the antigen on an APC. In your response use the following words (underline as you go write) – Helper T cell – APC – B cell, plasma cell – Antibody – Cytotoxic T cell – Cell mediated response – Humoral response © 2014 Pearson Education, Inc.
Main Idea Questions • Answer the following questions from your packet: – 5 a – 11 – 18 b – **26 a, b © 2014 Pearson Education, Inc.
Summary of the Humoral and Cell-Mediated Immune Responses § Both the humoral and cell-mediated responses can include primary and secondary immune responses § Memory cells enable the secondary response Animation: Immunology © 2014 Pearson Education, Inc.
Do now: §What is the difference between primary and secondary response? §Identify 2 differences between the primary and secondary response to antigen A §Which kinds of cells do you think might be involved in secondary response? © 2014 Pearson Education, Inc. §HW Reference: wkbk page 180 #4
Figure 35. 12 Antibody concentration (arbitrary units) Primary immune response to antigen A Secondary immune response to antigen A Primary immune response to antigen B 104 103 Antibodies to A 102 Antibodies to B 101 100 0 7 Exposure to antigen A 14 21 28 35 Exposure to antigens A and B Time (days) © 2014 Pearson Education, Inc. 42 49 56
Immunological Memory § The first exposure to a specific antigen represents the primary immune response § In the secondary immune response, memory cells facilitate a faster, stronger, and longer response § 10 -17 days vs 2 -7 days for antibody production § 3 X as much more antibodies produced § Immunological memory can span many decades § Q #24 from immunity classwork packet © 2014 Pearson Education, Inc.
Lesson #3: characteristics of the immune system §Immunological memory §Passive vs Active Immunity §Basis of transplant rejection §Allergies §Autoimmune disease © 2014 Pearson Education, Inc.
What kind of immunity is displayed here? Explain. (assume this is a vaccine) © 2014 Pearson Education, Inc.
Active Immunity (wkbk page 179, 180, 181) § Active immunity occurs when the body makes its own antibodies § Naturally: antigens enter the body § Artificially: induced when antigens are introduced into the body in vaccines § In this process of immunization, inactivated bacterial toxins or weakened or killed pathogens are introduced § Types of vaccines? § Inactivated § Attenuated- more effective § subunit © 2014 Pearson Education, Inc.
Food for thought: §Do you think society has a right to mandate vaccination on all its members? §Why or why not? © 2014 Pearson Education, Inc.
Explain why these are passive and identify which is artificial and which is natural © 2014 Pearson Education, Inc.
Passive Immunity § Passive immunity provides immediate, short-term protection § The body does not produce its own antibodies, they get it from somewhere else § Two kinds: § Naturally: § antibodies cross the placenta from mother to fetus § pass from mother to infant in breast milk § Artificially: § injecting antibodies into a nonimmune person ex: antivenom © 2014 Pearson Education, Inc.
Transplants § Cells transferred from one person to another can be attacked by the recipient’s immune defenses § When might cells be transferred from one person to the next? § This complicates blood transfusions and the transplant of tissues or organs § Why does this happen? ? ? © 2014 Pearson Education, Inc.
The MHC: Distinguishing Self from Non-Self § MHC codes for proteins on cell surfaces. § Class I MHC are located on all cells. The body does not recognize these receptors as foreign. § Class II MHC are on macrophages and plasma cells. § How to minimize rejection? § use donor tissue that closely matches the MHC molecules of the recipient § take medicines that suppress immune responses © 2014 Pearson Education, Inc.
Allergies (wkbk page 172) § Allergies are exaggerated (hypersensitive) responses to antigens called allergens § In localized allergies such as hay fever, plasma cells secrete antibodies specific for antigens on the surface of pollen grains § This triggers immune cells in connective tissue to release histamine and other inflammatory chemicals § Antihistamines block receptors for histamine and diminish allergy symptoms © 2014 Pearson Education, Inc.
Figure 35. 17 Ig. E Histamine Allergen 1 3 2 Granule Mast cell © 2014 Pearson Education, Inc.
Anaphylaxis § An acute allergic response can lead to anaphylactic shock, a life-threatening reaction § Triggers § bee venom, penicillin, peanuts, and shellfish § Treatment § Epipen- (contains epinepherine) © 2014 Pearson Education, Inc.
Autoimmune Diseases § In individuals with autoimmune diseases, the immune system targets certain molecules of the body § systemic lupus erythematosus, § rheumatoid arthritis § insulin-dependent diabetes mellitus § multiple sclerosis © 2014 Pearson Education, Inc.
Immune System Avoidance § Mechanisms to thwart immune responses have evolved in pathogens § Alteration of antigens § Dormancy § Attack the immune system © 2014 Pearson Education, Inc.
Alteration § A pathogen may alter how it appears to the immune system by antigenic variation § Flu § Sleeping sickness § HIV § How does this affect the immune system’s ability to fight off infection? © 2014 Pearson Education, Inc.
Dormancy § Some go about infecting cells and then entering an inactive state called latency § The virus (such as herpes simplex) remains latent until a stimulus reactivates it § Stimuli include stress, fever, or menstruation © 2014 Pearson Education, Inc.
Immune Attack (wkbk page 189) § Acquired immunodeficiency syndrome (AIDS) is caused by HIV (human immunodeficiency virus), which both attacks and escapes the immune system § It infects helper T cells with high efficiency § It escapes the immune system through its high mutation rate, which reduces the ability of the immune system to eliminate the infection § It also can undergo latency © 2014 Pearson Education, Inc.
Exit ticket §explain what is occuring in the immune system and why- use the words that follow the topic in your response § Allergies – mast cell, histamine § Transplant rejection – MHC, antibodies § AIDS- antigenic variation, helper T cell § Autoimmune disease- type 1 diabetes, MS © 2014 Pearson Education, Inc.
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