Chapter 24 The Immune System

Function of the Immune System Prevent pathogens from entering Eliminate pathogens from body Provide memory against future infections from same pathogen Pathogen = agent that causes disease © 2012 Pearson Education, Inc. 2

2 Divisions of Immune System INNATE (Non-specific) 1st line of defense; general response Quick to respond Prevent than eliminate Same response whether or not pathogen encountered before © 2012 Pearson Education, Inc. 3

2 Divisions of Immune System ADAPTIVE (Specific) Recognizes specific pathogens Slower to respond (1st time) Responsible for immune system memory Previous exposure to pathogen enhances immune response © 2012 Pearson Education, Inc. 4

INNATE IMMUNITY © 2012 Pearson Education, Inc. 5

Innate immunity (24.1–3) The response is the same Figure 24.1A Adaptive immunity (24.4–15) Found only in vertebrates; previous exposure to the pathogen enhances the immune response Innate immunity (24.1–3) The response is the same whetheror not the pathogen has Been previously encountered External barriers (24.1) Internal defenses (24.1–2) • Skin/ exoskeleton • Acidic environment • Secretions • Mucous membranes • Hairs • Cilia • Phagocytic cells • NK cells • Defensive proteins • Inflammatory response (24.2) • Antibodies (24.8–10) • Lymphocytes (24.11–13) Figure 24.1A An overview of animal immune systems The lymphatic system (24.3) 6

Some Components of Innate immunity Phagocytic cells Neutrophils and Macrophages, large cells that wander through the interstitial fluid and blood Destroy bacteria and virally-infected cells natural killer cells that attack cancer cells and virus-infected cells complement system, a group of proteins that recruit other immune responses Inflammation and Histamine Student Misconceptions and Concerns Students may be frustrated by the amount of detail about the immune system provided in this chapter, and struggle to organize information about the many types of cells and responses. Asking them to create or complete tables, similar to the one in Figure 24.1, can help your students manage the information presented in the textbook and in your class discussions. Teaching Tips 1. Students might be interested to learn that interferons are now mass-produced using recombinant DNA technology. Clinical studies are under way to explore their use in treating viral infections and cancer. 2. In an interesting article on the effectiveness of common hygiene methods, “Hygiene of the Skin: When Is Clean Too Clean?” Elaine Larson reviews the relationship between skin hygiene and infection. It can be found at the CDC website at www.cdc.gov/ncidod/eid/vol7no2/larson.htm. © 2012 Pearson Education, Inc. 7

Tissue injury; signaling molecules, such as histamine, are released. Figure 24.2_1 Pin Skin surface Bacteria Signaling molecules White blood cell Figure 24.2_1 The inflammatory response: tissue injury (part 1) Blood vessel 1 Tissue injury; signaling molecules, such as histamine, are released. 8

Phagocytes and fluid move into the area Figure 24.2_2 Blood clot Swelling Phagocytes and fluid move into the area Figure 24.2_2 The inflammatory response: phagocyte migration (part 2) 2 Dilation and increased leakiness of local blood vessels; phagocytes migrate to the area. 9

Figure 24.2_3 Phagocytes Figure 24.2_3 The inflammatory response: phagocytes consume bacteria (part 3) 3 Phagocytes (macrophages and neutrophils) consume bacteria and cellular debris; the tissue heals. 10

Lymphatic System Function Return tissue fluid back to CV system Fight infection As lymph circulates through lymphatic organs it collects pathogens transports them to lymphatic organs Here, macrophages engulf the invaders and lymphocytes may mount an adaptive immune response. Student Misconceptions and Concerns Students may be frustrated by the amount of detail about the immune system provided in this chapter, and struggle to organize information about the many types of cells and responses. Asking them to create or complete tables, similar to the one in Figure 24.1, can help your students manage the information presented in the textbook and in your class discussions. Teaching Tips 1. Excessive amounts of iron in the human body can promote bacterial infections and other disease. Searching for the key words iron supplements bacteria on the CDC website at www.cdc.gov will turn up many articles on this subject. 2. During a medical examination, a physician might feel for tenderness in the throat, axillary (armpit), and inguinal (groin) regions. Students are unlikely to appreciate the significance of this part of the exam. Making this connection for them can add relevance to your class discussions and generate additional interest in the subject. © 2012 Pearson Education, Inc. 11

Figure 24.3 Organs Adenoid Lymphatic ducts that drain into veins Lymph node Tonsils Lymph nodes Masses of lymphocytes and macrophages Thymus Lymphatic vessels Valve Lymphatic vessel Spleen Blood capillary Tissue cells Interstitial fluid Appendix Bone marrow Figure 24.3 The human lymphatic system Lymphatic capillary http://media.pearsoncmg.com/bc/bc_0media_bio/blast/index.htm?innate_immunity 12

ADAPTIVE IMMUNITY Responsible for specific response and immune system memory © 2012 Pearson Education, Inc. 13

24.4 The adaptive immune response counters specific invaders Our immune system responds to foreign molecules called antigens Antigens are molecules that elicit the adaptive immune response, Example: proteins or large polysaccharides on the surfaces of viruses or foreign cells The adaptive immune system reacts to specific pathogens “remembers” an invader. Student Misconceptions and Concerns 1. For students with limited science backgrounds, this section of the chapter can be particularly difficult; for some, it is the most challenging part of the textbook. Students must have a solid knowledge of the properties of different cells and their interactions, and understand that repeated exposure to antigens generates new interactions. The challenge is similar to explaining a new sport to someone unfamiliar to the game. (Imagine explaining the rules and strategies of football or poker to someone who had never heard of them.) Instructors might consider slowing their pace and using learning aids such as reference lists of cell types and their functions, or diagrams that remind students of these cellular interactions. 2. Having students read relevant material before it is addressed in lecture is one of the best ways to improve student comprehension. Before lecturing on a topic, identify specific textbook modules that should be read before you address them in class. Reading before lecture can lay a foundation that makes the lecture much more meaningful. However, it helps in other ways, too. As students listen in lecture, they know if definitions in lecture are included in the book, and students are already aware of which figures outline certain processes. 3. The concept of nonspecific and specific defenses is sometimes difficult for students new to the subject. Some analogies, such as the following, might help. Clothing can be considered a general defense against heat loss, minor surface abrasions, and minor chemical damage such as sunburn. Sunscreen is a specific defense, intended to limit exposure to ultraviolet radiation in particular. Teaching Tips The old saying “Give a man a fish and you have fed him for today; teach a man to fish and you have fed him for a lifetime” can be compared to the concept of passive and active immunity. Passive immunity, like the gift of a fish, is temporary. However, active immunity, like the ability to fish, can last a lifetime! © 2012 Pearson Education, Inc. 14

24.5 Lymphocytes mount a dual defense Lymphocytes are responsible for adaptive immunity, and originate from stem cells in the bone marrow. B lymphocytes or B cells continue developing in bone marrow. T lymphocytes or T cells develop further in the thymus. http://media.pearsoncmg.com/bc/bc_campbell_concepts_6/activities/cmr3Lib/activities/B24/B2401/st01/frame.html http://media.pearsoncmg.com/bc/bc_0media_bio/blast/index.htm?adaptive_immunity Student Misconceptions and Concerns 1. For students with limited science backgrounds, this section of the chapter can be particularly difficult; for some, it is the most challenging part of the textbook. Students must have a solid knowledge of the properties of different cells and their interactions, and understand that repeated exposure to antigens generates new interactions. The challenge is similar to explaining a new sport to someone unfamiliar to the game. (Imagine explaining the rules and strategies of football or poker to someone who had never heard of them.) Instructors might consider slowing their pace and using learning aids such as reference lists of cell types and their functions, or diagrams that remind students of these cellular interactions. 2. Having students read relevant material before it is addressed in lecture is one of the best ways to improve student comprehension. Before lecturing on a topic, identify specific textbook modules that should be read before you address them in class. Reading before lecture can lay a foundation that makes the lecture much more meaningful. However, it helps in other ways, too. As students listen in lecture, they know if definitions in lecture are included in the book, and students are already aware of which figures outline certain processes. Teaching Tips Many analogies can be developed relating to the cells and molecules involved in the immune response. In Module 24.5, the authors note that lymphocytes, which can respond to any antigen, resemble a standing army of soldiers in which each soldier is able to recognize a unique form of the enemy. © 2012 Pearson Education, Inc. 15

Each receptor can specifically bind to a unique antigen Key Point to Remember: Each B and T cell displays unique set of antigen receptors on cell surface Each receptor can specifically bind to a unique antigen Stem cell Bone marrow Via blood Immature lymphocytes Thymus Antigen receptors Via blood B cell T cell Final maturation of B and T cells in a lymphatic organ Figure 24.5A The development of B cells and T cells Lymph nodes, spleen, and other lymphatic organs Humoral immune response Cell-mediated immune response 16

Two different antibody molecules Figure 24.6 Antigen- binding site Two different antibody molecules Antigen molecule Antigenic determinant Figure 24.6 The binding of antibodies to antigenic determinants 17

24.5 Lymphocytes mount a dual defense Millions of distinct B and T cells each with different antigen receptors, capable of binding one specific type of antigen, Antibodies = antigen receptors of B cells T cell receptors = antigen receptors of T cells Antigenic determinants are specific regions on an antigen where antibodies bind. An antigen usually has several different determinants. Student Misconceptions and Concerns 1. For students with limited science backgrounds, this section of the chapter can be particularly difficult; for some, it is the most challenging part of the textbook. Students must have a solid knowledge of the properties of different cells and their interactions, and understand that repeated exposure to antigens generates new interactions. The challenge is similar to explaining a new sport to someone unfamiliar to the game. (Imagine explaining the rules and strategies of football or poker to someone who had never heard of them.) Instructors might consider slowing their pace and using learning aids such as reference lists of cell types and their functions, or diagrams that remind students of these cellular interactions. 2. Having students read relevant material before it is addressed in lecture is one of the best ways to improve student comprehension. Before lecturing on a topic, identify specific textbook modules that should be read before you address them in class. Reading before lecture can lay a foundation that makes the lecture much more meaningful. However, it helps in other ways, too. As students listen in lecture, they know if definitions in lecture are included in the book, and students are already aware of which figures outline certain processes. Teaching Tips Many analogies can be developed relating to the cells and molecules involved in the immune response. In Module 24.5, the authors note that lymphocytes, which can respond to any antigen, resemble a standing army of soldiers in which each soldier is able to recognize a unique form of the enemy. © 2012 Pearson Education, Inc. 18

24.5 Lymphocytes mount a dual defense B cells participate in the humoral immune response and secrete antibodies into the blood and lymph Attack pathogens OUTSIDE body cells!!!! T cells participate in the cell-mediated immune response, attack cells infected with bacteria or viruses, and Help bridge B-cell and Innate immune responses. http://media.pearsoncmg.com/bc/bc_0media_bio/blast/index.htm?adaptive_immunity Student Misconceptions and Concerns 1. For students with limited science backgrounds, this section of the chapter can be particularly difficult; for some, it is the most challenging part of the textbook. Students must have a solid knowledge of the properties of different cells and their interactions, and understand that repeated exposure to antigens generates new interactions. The challenge is similar to explaining a new sport to someone unfamiliar to the game. (Imagine explaining the rules and strategies of football or poker to someone who had never heard of them.) Instructors might consider slowing their pace and using learning aids such as reference lists of cell types and their functions, or diagrams that remind students of these cellular interactions. 2. Having students read relevant material before it is addressed in lecture is one of the best ways to improve student comprehension. Before lecturing on a topic, identify specific textbook modules that should be read before you address them in class. Reading before lecture can lay a foundation that makes the lecture much more meaningful. However, it helps in other ways, too. As students listen in lecture, they know if definitions in lecture are included in the book, and students are already aware of which figures outline certain processes. Teaching Tips Many analogies can be developed relating to the cells and molecules involved in the immune response. In Module 24.5, the authors note that lymphocytes, which can respond to any antigen, resemble a standing army of soldiers in which each soldier is able to recognize a unique form of the enemy. © 2012 Pearson Education, Inc. 19

Development of Immune System Memory by CLONAL SELECTION Legal Disclaimer: Clonal selection occurs in a similar manner for T cell-mediated immune memory (the following events are fictional - any resemblance to Historical characters is just coincidence - no B cells or Pathogens were actually harmed in the making of this animation. Student Misconceptions and Concerns 1. For students with limited science backgrounds, this section of the chapter can be particularly difficult; for some, it is the most challenging part of the textbook. Students must have a solid knowledge of the properties of different cells and their interactions, and understand that repeated exposure to antigens generates new interactions. The challenge is similar to explaining a new sport to someone unfamiliar to the game. (Imagine explaining the rules and strategies of football or poker to someone who had never heard of them.) Instructors might consider slowing their pace and using learning aids such as reference lists of cell types and their functions, or diagrams that remind students of these cellular interactions. 2. Having students read relevant material before it is addressed in lecture is one of the best ways to improve student comprehension. Before lecturing on a topic, identify specific textbook modules that should be read before you address them in class. Reading before lecture can lay a foundation that makes the lecture much more meaningful. However, it helps in other ways, too. As students listen in lecture, they know if definitions in lecture are included in the book, and students are already aware of which figures outline certain processes. Teaching Tips Our own learning experiences provide an analogy to the greater swiftness and intensity of a secondary immune response. When first presented with a problem, we may struggle to determine how best to respond. However, with that first experience behind us, we expect to respond more quickly and effectively when we meet that challenge again. Although in each circumstance we benefit from a certain type of memory (experiential in one case, chemical in the other) their mechanisms are quite different. Consider noting these similarities and differences in your class discussion of primary and secondary immune responses. © 2012 Pearson Education, Inc. 20

Every B cell displays unique antigen receptor on surface CLONAL SELECTION Primary immune response Antigen receptor on the cell surface B cells with different antigen receptors 1 Every B cell displays unique antigen receptor on surface Figure 24.7A_s1 Clonal selection of B cells: primary response (part 1, step 1) 21

Animation: Role of B Cells CLONAL SELECTION Primary immune response 2 Antigen molecules Antigen receptor on the cell surface B cells with different antigen receptors 1 Antigen only binds to B cell with complementary receptor Figure 24.7A_s2 Clonal selection of B cells: primary response (part 1, step 2) Animation: Role of B Cells 22

The selected B cell now divides rapidly!!! CLONAL SELECTION Primary immune response 2 Antigen molecules Antigen receptor on the cell surface B cells with different antigen receptors 1 3 First exposure to the antigen I WON THE ANTIGEN LOTTERY!! Figure 24.7A_s3 Clonal selection of B cells: primary response (part 1, step 3) The selected B cell now divides rapidly!!! 23

Plasma cells - secrete antibodies Memory cells Figure 24.7A_s4 Primary immune response 2 Antigen molecules Antigen receptor on the cell surface B cells with different antigen receptors 1 We’ll hang out And wait for the next invasion We’ll mark the Pathogen for Elimination!! 3 First exposure to the antigen Antibody molecules Figure 24.7A_s4 Clonal selection of B cells: primary response (part 1, step 4) 4 5 Plasma cells - secrete antibodies Memory cells 24

Secondary immune response Figure 24.7A_s5 Secondary immune response Alright boys, the pathogen is Back!! Looks like we’re in Charge of the second offensive - Get ready to divide!! Antigen molecules Second exposure to the same antigen Figure 24.7A_s5 Clonal selection of B cells: secondary response (part 2, step 1) Memory cells 25

Plasma cells Memory cells Secondary immune response Looks like we are off to fight This pathogen again! But now we can respond Faster with a larger army - those Bugs won’t know what hit them! Antibody molecules Plasma cells Memory cells divide Figure 24.7A_s6 Clonal selection of B cells: secondary response (part 2, step 2) Memory cells Memory cells 26

2nd response occurs quicker with greater magnitude!! Second exposure to antigen X, first exposure to antigen Y Secondary immune response to antigen X First exposure to antigen X Antibody concentration Primary immune response to antigen X Primary immune response to antigen Y Figure 24.7B The two phases of the adaptive immune response Antibodies to X Antibodies to Y 7 14 21 28 35 42 49 56 Time (days) 27

But what IS an Antibody????? Protein made of 4 separate subunits Protein made of 4 separate subunits Sits on surface of B cells until B cell stimulated to release antibodies into body fluids Student Misconceptions and Concerns 1. For students with limited science backgrounds, this section of the chapter can be particularly difficult; for some, it is the most challenging part of the textbook. Students must have a solid knowledge of the properties of different cells and their interactions, and understand that repeated exposure to antigens generates new interactions. The challenge is similar to explaining a new sport to someone unfamiliar to the game. (Imagine explaining the rules and strategies of football or poker to someone who had never heard of them.) Instructors might consider slowing their pace and using learning aids such as reference lists of cell types and their functions, or diagrams that remind students of these cellular interactions. 2. Having students read relevant material before it is addressed in lecture is one of the best ways to improve student comprehension. Before lecturing on a topic, identify specific textbook modules that should be read before you address them in class. Reading before lecture can lay a foundation that makes the lecture much more meaningful. However, it helps in other ways, too. As students listen in lecture, they know if definitions in lecture are included in the book, and students are already aware of which figures outline certain processes. Teaching Tips Challenge your class to explain the adaptive advantages of antibodies’ Y-shaped structure. Why aren’t antibodies just made up of a single heavy and a single light chain? (Biologists have theorized that the Y shape permits the bonding together of two antigens or antigen-presenting surfaces, allowing a chain reaction or form of clumping.) © 2012 Pearson Education, Inc. 28

Light chain Heavy chain Figure 24.8A Figure 24.8A A computer graphic of an antibody molecule 29

Antigen-binding sites Figure 24.8B Antigen Antigen-binding sites V V V V C C Light chain Antigen-binding site VARIES between each unique antibody C C Figure 24.8B Antibody structure and the binding of an antigen-binding site to its complementary antigen (enlargement) Heavy chain The CONSTANT region defines Ab class and effector action V = variable C = constant 30

Antibodies mark antigens for elimination Binding of antibodies to antigens inactivates antigens by Neutralization (blocks viral binding sites; coats bacteria) Agglutination of microbes Precipitation of dissolved antigens Activation of the complement system Complement molecule Bacteria Virus Antigen molecules Bacterium Foreign cell Hole Enhances Leads to Figure 24.9 Effector mechanisms of the humoral immune response Phagocytosis Cell lysis Macrophage Animation: Antibodies 31

T cell mediated immune function T-Cells Detect presence of foreign antigens on SURFACE of virally or bacterially infected body cells 2 types of T cells: Helper T cells -- stimulate B-cell and T-cell mediated immune responses Cytotoxic T cells DESTROY infected cells as marked by Helper T cells Student Misconceptions and Concerns 1. For students with limited science backgrounds, this section of the chapter can be particularly difficult; for some, it is the most challenging part of the textbook. Students must have a solid knowledge of the properties of different cells and their interactions, and understand that repeated exposure to antigens generates new interactions. The challenge is similar to explaining a new sport to someone unfamiliar to the game. (Imagine explaining the rules and strategies of football or poker to someone who had never heard of them.) Instructors might consider slowing their pace and using learning aids such as reference lists of cell types and their functions, or diagrams that remind students of these cellular interactions. 2. Having students read relevant material before it is addressed in lecture is one of the best ways to improve student comprehension. Before lecturing on a topic, identify specific textbook modules that should be read before you address them in class. Reading before lecture can lay a foundation that makes the lecture much more meaningful. However, it helps in other ways, too. As students listen in lecture, they know if definitions in lecture are included in the book, and students are already aware of which figures outline certain processes. Teaching Tips 1. The authors note that the recognition by a helper T cell of a self protein and a foreign antigen in combination is like the two-key system used by banks to access safe-deposit boxes. 2. Your students might find the descriptions in Modules 24.11 and 24.12 to be particularly confusing, as the interactions of many cell types are described. Figures 24.11 and 24.12 help to simplify the details of these interactions. Video: T Cell Receptors © 2012 Pearson Education, Inc. 32

The humoral immune response: Figure 24.UN01 The humoral immune response: makes which bind to B cell Antibodies Antigens in body fluid The cell-mediated immune response: Infected body cell Figure 24.UN01 Reviewing the Concepts, 24.5 T cell Self-nonself complex 33

Infected body cells will display antigens of pathogen on cell surface Humoral immune response (secretion of antibodies by plasma cells) Phagocytic cell (yellow) engulfing a foreign cell Self-nonself complex B cell Interleukin-2 stimulates cell division T cell receptor Microbe Macrophage 3 5 6 Interleukin-2 activates B cells and other T cells 1 2 Helper T cell 4 7 Self protein Cell-mediated immune response (attack on infected cells) Binding site for the self protein Antigen-presenting cell Cytotoxic T cell Antigen from the microbe (nonself molecule) Figure 24.11 The activation of a helper T cell and its roles in immunity Binding site for the antigen Helper T cells are trained to recognize foreign antigens and alert B cells and Cytotoxic T cells 34

How are B and T cells trained to recognize ‘self’ vs How are B and T cells trained to recognize ‘self’ vs. ‘non-self’ antigens???? Each of us display a unique protein and carbohydrate ‘fingerprint’ on the surface of our cells This fingerprint is referred to as the MHC protein complex During development, B and T cells are exposed to MHC (major proteins Any B or T cells that have antigen receptors that can bind to ‘self’ antigens are DESTROYED!! This is called CLONAL DELETION. Student Misconceptions and Concerns 1. For students with limited science backgrounds, this section of the chapter can be particularly difficult; for some, it is the most challenging part of the textbook. Students must have a solid knowledge of the properties of different cells and their interactions, and understand that repeated exposure to antigens generates new interactions. The challenge is similar to explaining a new sport to someone unfamiliar to the game. (Imagine explaining the rules and strategies of football or poker to someone who had never heard of them.) Instructors might consider slowing their pace and using learning aids such as reference lists of cell types and their functions, or diagrams that remind students of these cellular interactions. 2. Having students read relevant material before it is addressed in lecture is one of the best ways to improve student comprehension. Before lecturing on a topic, identify specific textbook modules that should be read before you address them in class. Reading before lecture can lay a foundation that makes the lecture much more meaningful. However, it helps in other ways, too. As students listen in lecture, they know if definitions in lecture are included in the book, and students are already aware of which figures outline certain processes. Teaching Tips Students may enter your course knowing that the best types of tissue transplants are from a closely matched donor. However, what does it mean to have a tissue “match”? Few students can explain the specific reasons behind the need for tissue matching, or how such matching is done. Challenge your students to explain why we try to ensure a match between the tissues of a donor and a recipient. By posing such general questions, instructors can raise interest in the specific details of the answers. © 2012 Pearson Education, Inc. 35

WHAT is MHC? The major histocompatibility complex (MHC) is a set of cell surface molecules encoded by a large gene family in all vertebrates. MHC molecules mediate interactions of WBC with other leukocytes or body cells. MHC determines compatibility of donors for organ transplant as well as one's susceptibility to an autoimmune disease via cross reacting immunization. In humans, MHC is also called human leukocyte antigen (HLA).

The immune system depends on our molecular fingerprints “Self” is signaled by major histocompatibility complex (MHC), a group of proteins unique to the individual that is present on the surface of cells Can cause rejection of transplanted organs

Mechanism of HIV action Transmitted through body fluids Inside the body, HIV binds to and enters helper T cells RNA genome of HIV is reverse-transcribed inside the T cells Newly produced DNA is integrated into host T cell's genome, able to direct the production of new viruses HIV in the bloodstream may infect and kill other helper T cells http://media.pearsoncmg.com/bc/bc_campbell_concepts_6/activities/c6eLib/activities/H18/H1804/st01/frame.html

DISORDERS OF THE IMMUNE SYSTEM Malfunction or failure of the immune system causes disease In autoimmune diseases, the immune system turns against some of the body's own molecules In immunodeficiency diseases, immune system components are lacking, and infections occur frequently Physical and emotional stress may weaken the immune system Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

DISORDERS OF THE IMMUNE SYSTEM Rheumatoid arthritis Autoimmune diseases The system turns against the body’s own molecules Examples: Rheumatic fever, Type I Diabetes, Multiple Sclerosis, Rheumatoid arthritis, Lupus

DISORDERS OF THE IMMUNE SYSTEM HIV on a lymphocyte Immunodeficiency diseases Immune components are lacking, and infections recur Ex: Acquired immune deficiency syndrome (AIDS) SCIDS

Animation: HIV Reproductive Cycle Immunodeficiency HIV destroys helper T cells, compromising the body's defenses HIV (human immunodeficiency virus) causes AIDS Most often attacks helper T cells Destruction of humoral and cell-mediated immunity compromises body's ability to fight infections HIV is transmitted mainly in blood and semen Animation: HIV Reproductive Cycle

DISORDERS OF THE IMMUNE SYSTEM Allergies are overreactions to certain environmental antigens called allergens : Ex. Animal dander, dust mites, pollen release of histamine causes symptoms Antihistamines can relieve symptoms anaphylactic shock: life threatening reaction to injected or ingested allergens.

B cell (plasma cell) Mast cell Antigenic determinant Histamine Allergen (pollen grain) enters blood stream B cells make antibodies Antibodies attach to mast cell Allergen binds to antibodies on mast cell Histamine is released, causing allergy symptoms Sensitization: Initial exposure to allergen Later exposure to same allergen

The chain of events in the local inflammatory response: A. The cell is damaged B. Chemical alarm signals (histamines) are released C. Defenses are mobilized D. Blood vessels leak E. This attracts phagocytes F. Phagocytes squeeze into the tissue spaces G. Increase in blood flow and fluid causes redness, heat and swelling H. This disinfects the injured tissue I. The white cells engulf the bacteria and any body cells injured in the attack – pus is dead WBCs J. The blood localizes the inflammation Blood clot Swelling Phagocytes and fluid move into the area

Summary