Immunity
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Transcript of Immunity
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Immunity
Chapter 10
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Early Advances
• Edward Jenner developed vaccine against smallpox
• Pasteur demonstrated that heating could kill microorganisms in food and beverages
• Koch linked a microorganism with a specific disease (anthrax)
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Three Lines of Defense
• Barriers at body surfaces
• Nonspecific responses
• Immune responses
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Barriers at Body Surface
• Intact skin and mucous membranes
• Lysozyme
• Normal bacterial flora
• Flushing effect and low pH of urine
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Nonspecific Responses
• Lymph nodes trap and kill
pathogens
• Natural killer cells attack a
range of targets
• Inflammation
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Complement System
• Plasma proteins that take part in both specific and nonspecific response
• Activation of one triggers cascade of reactions that activate others
CASCADE REACTION
FORMATION OFATTACK COMPLEXES
LYSIS OFTARGET
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Acute Inflammation
• Nonspecific response to foreign invasion,
tissue damage, or both
• Destroys invaders, removes debris, and
prepares area for healing
• Characterized by redness, swelling,
warmth, and pain
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Inflammation
• Mast cells release histamine• Capillaries dilate and leak• Complement proteins attack bacteria• White cells attack invaders and clean up
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Features of Immune Responses
• Self/nonself recognition
• Specificity
• Diversity
• Memory
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Antigens
• “Nonself” markers on foreign agents and altered body cells such as tumors
• Trigger division of B and T cells
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Memory and Effector Cells
• When a B or T cell is stimulated to divide,
it produces more than one cell type
• Memory cells are set aside for future use;
they are the basis for immune memory
• Effector cells engage and destroy the
current threat
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Steps in Immune Response
• Recognition of an antigen
• Rounds of cell division that form huge
populations of lymphocytes
• Specialization of lymphocytes into
effector and memory cells that have
receptors for one kind of antigen
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Key Components of Immune Response
• MHC markers
• Antigen-presenting cells
• T cells
• B cells
• Natural killer cells
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Overview of Interactions
Naive helper T cell
Naive B cell
Antigen-presenting cell
Activated helper T cell
Effector B cell
Naive cytotoxic T cell
Effector cytotoxic T cell
Antibody-mediated response
Cell-mediated response
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B and T Cell Specificity
• All the antigen receptors of a given B or
T cell are identical
• B cells acquire unique antigen-binding
receptors in marrow
• T cells acquire unique antigen-binding
receptors in thymus
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Clonal Selection
• Only the B cell with antigen-receptor that matches antigen is stimulated to divide
• Mitosis yields many cells with that receptor
antigen
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Immunological Memory
• Memory cells specific for an antigen are quickly activated to divide upon subsequent exposure to that antigen
Primary Immune Response:
SecondaryImmune Response:
effector cells memory cells
effector cells memory cells
naïve T or B cell
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Lymphocyte Battlegrounds
• Lymph nodes filter antigens from body fluids
• Macrophages, dendritic cells, B and T cells in nodes and spleen mount a defense
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Antibody-Mediated Response
• Carried out by B cells
• Targets are intracellular pathogens and
toxins
• Antibodies bind to target and mark it for
destruction by phagocytes and
complement
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Antibody Structure
• Antibody consists of four polypeptide chains
• Certain parts of each chain are variable; impart antigen specificity
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Antibody- Mediated Response
Naive B cell
Antigen-presentingB cell
Helper T cell
Interleukins
Memory B cell
Effector B cellsecretes antibodies
• Virgin B cell becomes antigen-presenting B cell
• Helper T cell binds to antigen-MHC complex on the B cell
• Interleukins stimulate B cell division and differentiation
• Effector cells secrete antibodies
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5 Classes of Immunoglobulins
IgG, IgD, and IgE IgA IgM
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Cell-Mediated Response
One macrophage
Another macrophage
interleukins
interleukins Helper T cell
Cytotoxic T cell
Infected body cell
• Carried out by T cells
• Stimulated by antigen-
presenting macrophages
• Main target is antigen-
presenting body cells
(cells with intracellular
pathogens) or tumor cells
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Organ Rejection
• Cytotoxic T cells can contribute to rejection of transplanted tissue
• They recognize a portion of the donor cell’s MHC complex as self, view a portion as foreign
• Treat the combination as an antigen-MHC complex and attack donor cells
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Monoclonal Antibodies
• Manufacture antibodies against tumor-
specific antigens
• First created by fusing antigen-producing
B cells from mice with cells from B cell
tumors
• Now made in genetically engineered cells
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Lymphokine-Activated Killers
• Lymphocytes are extracted from tumors
• Extracted cells are exposed to a
lymphokine, an interleukin
• Large population of tumor-infiltrating,
activated lymphocytes is then reinjected
into patient
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Immunization
• Process that promotes immunity
• Active immunization - – Antigen-containing material is injected
– Confers long-lasting immunity
• Passive - – Purified antibody is injected
– Protection is short lived
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Allergies
• Immune reaction to a harmless substance
• Genetic predisposition
• IgE responds to antigen by binding to mast cells and basophils
• These cells secrete the substances that cause symptoms
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Anaphylactic Shock
• A life-threatening allergic reaction
• Caused by the release of histamine by
many mast cells and basophils
• Airways constrict and blood pressure
drops as capillary permeability soars
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Autoimmune Disorders
• Immune system makes
antibodies against self
antigens
• Grave’s disease
• Myasthenia gravis
• Rheumatoid arthritis
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SCIDs
• Severe combined immunodeficiency
• Body’s ability to make lymphocytes is impaired or nonexistent
• High vulnerability to infection
• ADA deficiency is a heritable SCID
• Has been successfully treated using gene therapy