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Transcript
Chapter 18 The Immune System Human immunodeficiency viruses budding from a T cell An overview of animal immune systems Adaptive immunity Innate immunity The response is the same whether or not the pathogen has been previously encountered External barriers • Skin/ exoskeleton • Acidic environment • Secretions • Mucous membranes • Hairs • Cilia Found only in vertebrates; previous exposure to the pathogen enhances the immune response Internal defenses • Phagocytic cells • NK cells • Defensive proteins • Inflammatory response • Antibodies • Lymphocytes The lymphatic system Cell mediating immune responses (1) Cell mediating immune responses (2) Features of selected cytokines The inflammatory responses An innate body defense in vertebrates caused by a release of histamine and other chemical alarm signals that trigger increased blood flow, a local increase in white blood cells, and fluid leakage from the blood. The resulting inflammatory response includes redness, heat, and swelling in the affected tissues. Pin Skin surface Swelling Bacteria Histamine Complement system Blood clot Phagocytes and fluid move into the area Signaling molecules Phagocytes White blood cell Blood vessel 1 Tissue injury; signaling molecules, such as histamine, are released. 2 Dilation and increased leakiness of local blood vessels; phagocytes migrate to the area. 3 Phagocytes (macrophages and neutrophils) consume bacteria and cellular debris; the tissue heals. Sequence of events in a localized innate inflammatory response to bacteria Some important local inflammatory mediators polypeptides (bradykinin, kallikrein) Macrophages contracting bacteria and preparing to engulf them Phagocytosis and intracellular destruction of a microbe Exocytosis Role of phagocytosis in innate immune responses Function of complement C3b as an opsonin Non-specifically binding Specifically binding Functions of complement proteins Role of type I interferon in preventing viral replication endocrine autocrine paracrine Anatomy of a lymph node Derivation of B cells and T cells Summary of the role of B, cytotoxic T, and helper T cells in immune responses Humoral immunity and Cellular immunity Two types of adaptive immune responses The humoral immune response: makes which bind to B cell Antibodies The cell-mediated immune response: T cell Infected body cell Self-nonself complex Antigens in body fluid Immunoglobin structure Disulfide bond -S—S- Memory of the adaptive immune response Clonal selection of B cells in the primary and secondary immune response Primary immune response 2 1 B cells with different antigen receptors Secondary immune response Antigen molecules Antigen receptor on the cell surface Antibody molecules 3 First exposure to the antigen Cell activation: growth, division, and differentiation Antigen molecules Antibody molecules 4 6 Second exposure 5 to the same antigen First clone Endoplasmic reticulum Plasma (effector) cells secreting antibodies Second clone Clone of plasma (effector) cells secreting antibodies Memory cells Clone of memory cells The two phases of adaptive immune response Antibody concentration Second exposure to antigen X, first exposure to antigen Y Secondary immune response to antigen X First exposure to antigen X Primary immune response to antigen X Primary immune response to antigen Y Antibodies to Y Antibodies to X 0 7 14 21 35 28 Time (days) 42 49 56 Summary of events in antibody-mediated immunity against bacteria Primary lymphoid organs: thymus, bone marrow Secondary lymphoid organs: spleen, lymphoid nodes Sequence of events by which antigen is possessed and presented to a helper T cell by macrophage or a B cell Three events are required for the activation of helper T cells APC Processing and presentation of viral antigen to a cytotoxic T cell by an infected cell By proteasomes The activation of a helper T cell and its role in immunity Phagocytic cell (yellow) engulfing a foreign cell Self-nonself complex Macrophage Microbe B cell T cell receptor Interleukin-2 stimulates cell division 5 3 1 2 Helper T cell 4 6 7 Interleukin-2 activates B cells and other T cells Self protein Antigen from the microbe (nonself molecule) Antigen-presenting cell Binding site for the self protein Interleukin-1 stimulates the helper T cell Binding site for the antigen Humoral immune response (secretion of antibodies by plasma cells) Cytotoxic T cell Cell-mediated immune response (attack on infected cells) How a cytotoxic T cell kills an infected cells 1 A cytotoxic T cell binds to an infected cell. 2 Perforin makes holes in the infected cell’s membrane, and an enzyme that promotes apoptosis enters. Self-nonself complex Infected cell Perforin molecule A hole forming Foreign antigen Cytotoxic T cell Enzymes that promote apoptosis 3 The infected cell is destroyed. Activation of helper T cells and cytotoxic T cells MHC restriction of the lymphocyte receptors Summary of events by which a bacteria infection leads to antibody synthesis in secondary lymphoid organs Direct enhancement of phagocytosis by antibody Activation of classical complement pathway by binding of antibody to bacterial antigen Membrane attack complex Rate of antibody production following initial exposure to an antigen and subsequent exposure to the same antigen Summary of events in the killing of virus-infected cells by cytotoxic T cells Role of IL-12 and interferon-gamma, secreted by activated helper T cells, in stimulating the killing ability of NK cells and macrophages Summary of host responses to virus Systemic responses to infection or injury (the acute phase response) Inhibits immune responses Role of macrophage in immune responses Human ABO blood groups Major types of hypersensitivity Immediate hypersensitivity allergic response Mast cell Characteristic butterfly or malar rash in a patient with systemic lupus erythematosus Malfunction or failure of the immune system causes disease Autoimmune diseases occur when the immune system turns against the body’s own molecules. Examples of autoimmune diseases include - lupus. - rheumatoid arthritis. - insulin-dependent diabetes mellitus. - multiple sclerosis. Factors for autoimmune diseases - Gender. - Genetics. - Environment. B cell B cell Lupus Rheumatoid arthritis Tc cell Tc cell Multiple sclerosis Insulin-dependent diabetes mellitus Some possible causes of autoimmune attack Immunodeficiency disease Immunodeficiency diseases occur when an immune response is - defective. - absent. SCID: severe combined immunodeficiency. “Bubble boy” Immunodeficiency acquired in life. - AIDS. - Hodgkin’s disease (Hodgkin’s lymphoma). The immune system may be weakened by - physical stress. - emotional stress. (Students are more likely to be sick during a week of exams) HIV destroys helper T cells, compromising the body’s defenses AIDS (acquired immunodeficiency syndrome), results from infection by HIV, the human immunodeficiency virus. The AIDS virus usually attacks helper T cells, impairing the - cell-mediated immune response. - humoral immune response. - opening the way for opportunistic infections. A human helper T cell (red) under attack by HIV (blue dots) AIDS patients typically die from - opportunistic infections. - cancers. The rapid evolution of HIV complicates AIDS treatment HIV mutates very quickly. Natural New strains are resistant to AIDS drugs. Drug-resistant strains now infect new patients. Dr. David Da-I Ho selection! A “cocktail” of three separate drugs, the current treatment for people living with HIV Allergies are overreactions to certain environmental antigens Allergies are hypersensitive (exaggerated) responses to otherwise harmless antigens in our surroundings. Antigens that cause allergies are called allergens. Allergic reactions typically occur - very rapidly. - in response to tiny amounts of an allergen. Allergic reactions can occur in many parts of the body, including - nasal passages. - bronchi. - skin. Symptoms of allergic reactions - sneezing. - runny nose. - coughing. - wheezing. - itching. The two stages of an allergic reaction Sensitization: Initial exposure to an allergen Later exposure to the same allergen B cell (plasma cell) Mast cell Antigenic determinant 1 An allergen (pollen grain) enters the bloodstream. Histamine 2 B cells make antibodies. 3 Antibodies attach to a mast cell. 4 The allergen binds to antibodies on a mast cell. 5 Histamine is released, causing allergy symptoms. Anaphylactic shock An “epi pen” for counteraction of anaphylactic shock A mini-glossary of cells and chemical mediators involved in immune functions (1) A mini-glossary of cells and chemical mediators involved in immune functions (2) A mini-glossary of cells and chemical mediators involved in immune functions (3)