Bio Chap 51 - Immune System
Recall the infectious agent that causes AIDS and explain how it weakens the immune system.
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Distinguish between active and passive immunity.
1. Active immunity: long-lasting immunity conferred by the action of B cells and T cells and the resulting B and T memory cells specific for a pathogen. Active immunity can develop as a result of natural infection or immunization. 2. Passive immunity: short-term immunity conferred by the transfer of antibodies, as occurs in the transfer of maternal antibodies to a fetus or nursing infant.
Compare and contrast the structure and function of an enzyme's active site and an antibody's antigen-binding site.
1. Antibodies coat free virus particles 2. The virus cannot bind to the host cell's plasma membrane 3. The antibody-coated virus is recognized, phagocytized, and destroyed by a neutrophil or macrophages.
Describe several systemic reactions to infection, and explain how they contribute to defense.
- A minor injury or infection causes a local inflammatory response, but severe tissue damage or infection may lead to a response that is systemic. Cells in injured or infected tissue often secrete molecules that stimulate the release of additional neutrophils from bone marrow. -Fever; in response to certain pathogens, substances released by activated macrophages cause the body's thermostat to reset to a higher temperature. Elevated body temperature may enhance phagocytosis, speed up chemical reactions, and accelerate tissue repair. -Septic Shock: very high fever, low blood pressure, and poor blood flow through capillaries (life threatening conditions).
List several chemical signals that initiate and mediate the inflammatory response
- Histamine: produced by mast cells; is received by blood vessels, constricts blood vessels at wound site and dilates blood vessels -Chemokines: produced by injured tissues and macrophages in tissues; is received by neutrophils and macrophages; mark path to wound + promote dilation and increased permeability of blood vessels -Cytokines: produced by macrophages; received by leukocytes, bone marrow, CNS, and local tissues; mark path to wound + increase production of macrophages & neutrophils + induce fever by increasing set point for control of body temperature + stimulate cells involved in wound repair
Explain what is meant by the nonspecific defense/innate immunity, and list the nonspecific lines of defense in the vertebrate body.
- Innate Immunity is a form of defense common to all animals that is active immediately upon exposure to pathogens and that is the same whether or not the pathogen has been encountered previously. Cells involved in innate immunity respond in the same way to all antigens -Examples are: 1) barrier defenses: skin, mucous membranes, and secretions. 2) Internal defenses: phagocytic cells, natural killer cells, antimicrobial proteins, and inflammatory response.
List some known autoimmune disorders, and describe possible mechanisms of autoimmunity
- Multiple Sclerosis -Rheumatoid Arthritis -Type 1 Diabetes Anti-self T and B cells aren't destroyed before they mature, causing them to trigger an immune response to a self-molecule
Describe an allergic reaction including the role of IgE, mast cells, and histamine.
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Describe an antigen-presenting cell (APC)
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Describe the cellular basis for immunological memory.
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Describe the cellular basis for self-tolerance.
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Describe the function of supressor T cells
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Describe the potential problem of Rh incompatibility between a mother and her unborn fetus, and explain what precautionary measures may be taken.
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Describe the rejection process of transplanted tissue in terms of normal cell-mediated immune response, and describe how the immune system can be suppressed in transplant patients.
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Describe why immunodeficient individuals are more susceptible to cancer.
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Design a flow chart describing the sequence of events that follows the interaction between antigen presenting macrophages and helper T cells, including both cell-mediated and humoral immunity.
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Distinguish between T-independent antigens and T-dependent antigens.
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Explain how the humoral response is provoked.
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Explain how the immune response to Rh factor differs from the response to A and B antigens.
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Explain why, other than with identical twins, it is virutally impossible for two people to have identical MHC markers.
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For ABO blood groups, list all possible combinations for donor and recipient in blood transfusions; indicate which combinations would cause an immune response in the recipient; and state which blood type is the universal donor.
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Explain how the function of cytotoxic T cells differs from that of complement and natural killer cells.
type of cytotoxic lymphocyte critical to the innate immune system. The role NK cells play is analogous to that of cytotoxic T cells in the vertebrate adaptive immune response. NK cells provide rapid responses to virally infected cells and respond to tumor formation, acting at around 3 days after infection. Typically immune cells detect MHC presented on infected cell surfaces, triggering cytokine release, causing lysis or apoptosis. NK cells are unique, however, as they have the ability to recognize stressed cells in the absence of antibodies and MHC, allowing for a much faster immune reaction. They were named "natural killers" because of the initial notion that they do not require activation in order to kill cells that are missing "self" markers of major histocompatibility complex (MHC) class 1.
Explain how the immune response differs from nonspecific defenses.
Immune response is specific, systemic and re-callable. Nonspecific defenses are immediate.
Describe a plausible mechanism for how interferons can fight viral infections and might act against cancer
Interferons are proteins that has antiviral or immune regulatory functions. Interferon-alpha and interferon-beta, secreted by virus-infected cells, help nearby cells resist viral infection; interferon-y, secreted by T cells, helps activate macrophages.
List two types of phagocytic cells derived from white blood cells.
Macrophages and neutrophils -Neutrophil is the most abundant type of white blood cell. Tend to self-destruct as they destroy invaders, limiting their life span to a few days. Circulate in the blood, and are attracted by signals from infected tissues and then engulf and destroy the infecting pathogens. Has granules that contain pathogen-killing molecules. -Macrophages are present in many tissues that functions in innate immunity by destroying microbes and inacquired immunity as an antigen-presenting cell. Recruit other cells and ingest and kill pathogens. Have pseudopodia to engulf bacteria, and lysosomes to digest bacteria.
Explain how the function of natural killer cells differs from the function of phagocytes
Natural killer cell is a type of WBC that can kill tumor cells and virus-infected cell as part of innate immunity. They differ from phagocytes because they do not engulf stricken cells. Instead, they release chemicals that lead to cell death, inhibiting further spread of the virus or cancer.
Explain how complement proteins may be activated and how they function in cooperation with other defense mechanisms.
~ 30 blood proteins amplify the inflammatory response, enhance phagocytosis, or directly lyse extracelluar pathogens.
Explain how the inflammatory response prevents the spread of infection to surrounding tissue
The clotting cascade keeps bacteria close to the phagocytes, helps stop any bleeding, and prevents the spread of infection or inflammation.
Distinguish between variable (V) regions and constant (C) regions of an antibody molecule
V regions are adjacent and face away from the plasma membrane. The unique, high variable amino acid sequences in the V regions of every BCR and TCR allow each of them to bind to a unique epitope.
Explain how B cells are activated.
1. B cells recognizes invader. Processes the foreign molecule, and present it on the surface by an MHC class II protein. 2. B Cells is activates helper T Cell. The MHC pptide complex interacts with complementary receptors on a help T cell, activating it. 3. B Cell is activated by helper T cells. Cytokines from the activated helper T cell activate the B cell.
Describe the mechanism of clonal selection.
1. Each lymphocyte has thousands of copies of a unique receptor on its surface. The receptor, a membrane protein, recognizes only one antigen. 2. The lymphocyte is activated when it binds to its specific antigen. 3. An activated lymphocyte divides and makes many identical copies of itself. In this way, specific cells are selected and cloned in response to an infection. 4. Some of the cloned cells descended from an activated lymphocyte persist after the pathogen is eliminated and allow a rapid response if the infection recurs.
Explain how humoral immunity and cell-mediated immunity differ in their defensive activties
1. Humoral (antibody-mediated) immune response: Defend against extracellular pathogens in blood and lymph by binding to antigens, thereby neutralizing pathogens and making them better targets for phagocytic cells and complement proteins. Involves the activation of B cells and leads to the production of antibodies, which defend against bacteria and viruses in body fluids. 2. Cell-Mediated Immunity: defend agaisnt intracellular pathogens and cancer by binding to and lysing the infected cells or cancer cells. Involves the activation of cytotoxic T cells
List the five major classes of antibodies/immunoglobin in mammals and distinguish among them.
1. IgG 2. IgD 3. IgA 4. IgE 5. IgM
Distinguish between primary and secondary immune response.
1. Primary response is the intial adaptive response of B cells and T cells 2. Secondary immune response is when activated B cells and T cells produce specialized daughter cells called memory cells in response to when the same antigen enters the body again. Secondary response is faster and more efficient than the primary response.
What are the four key characteristic of the adaptive immune response?
1. Specificity 2. Diversity 3. Memory 4. Self-nonself recognition
Describe the inflammatory response including how it is triggered
1. When skin breaks, pathogens enter a wound. 2. Platelets release blood-clotting proteins at the wound site. 3. Wound tissues and macrophages at the wound site secrete chemokines, signaling molecules that recruit immune cells by forming a gradient to mark the path to the site. 4. Mast cells release chemical messengers that constrict blood vessels near the wound - reducing blood flow and thus blood loss. Mast cells also secrete histamine and other signaling molecules, which constrict blood vessel at wound but dilate blood vessels near wound. 5. Neutrophils and macrophages remove pathogens by phagocytosis - engulfing and digesting foreign particles. Macrophages secretes chemical messengers called cytokines that attract other immune system cells to the site, stimulate bone marrow to make and release additional phagocytes, induce fever, and activate cells involved in repair and wound healing.
Define phagocytosis
A type of endocytosis in which large particulate substancees or small organisms are taken up by a cell. It is carried out by certain immune cells of animals.
Outline the development of B and T lymphocytes from stem cells in red bone marrow.
All lymphocytes and blood cells are produced from stem cells in the bone marrow
Explain how T-cell receptors recognize "self" and how macrophages, B cells, and some T cells recognize one another in interactions.
All nucleated cells are capable of presenting "Self" proteins through MHC Class I proteins on their surface.
Characterize antigen molecules, in general, and explain how a single antigen molecule may stimulate the immune system to produce several different antibodies.
An antigen is any foreign molecules that can initiate an immune system response. Antibodies are proteins that are produced and secreted by certain lymphocytes and that bind only to a specific part of a specific antigen
Diagram and label the structure of an antibody, and explain how this structure allows antibodies to perform the following functions: (1) recognize and bind to antigens, and (2) assist in destruction and elimination of antigens.
An antigen receptor of a B Cell binds to an epitope, a particular part of an antigen. Following binding, the B cell gives rise to cells that secrete a soluble form of the antigen receptor. This soluble receptor, called an antibody, is specific for the same epitope as the original B cell. Different antibodies can recognize distinct epitopes on the same antigen. Furthermore, antibodies can recognize free antigens as well as antigens on a pathogen's surface.
Describe where T and B cells migrate, and explain what happens when they are activated by antigens
B cells mature in the bone marrow, and T cells mature in the Thymus. Lymphocytes recognize antigens and become activated in the spleen and lymph nodes. They are then transported throughout the lymphatic system.
Explain how the physical barrier of skin is reinforced by chemical defenses
Chemical secretions, such as oil secreted by skin cells, is converted to fatty acids by bacterial cells that live on the surface. Fatty acids lower the pH of the skin surace to about 5, creating a dry, acidic environment that prevents the growth of most bacterial specifies that might be a threat to the body.
Describe how cytotoxic T cells recognize and kill their targets
Cytotoxic (killer) T cells bind to the antigen presented by MHC Class I proteins on the surface of infected cells and kill them.
