Chapter 15:Adaptive Immune Response
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Transcript of Chapter 15:Adaptive Immune Response
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Chapter 15:Adaptive Immune Response
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General Characteristics
• Involves specialized WBC’s known as lymphocytes
• Response is highly specific, evolves throughout an organisms life-time
• Response generates memory• Can discriminate between HEALTHY self and
non-self OR between HEALTHY self and DAMAGED self
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The Adaptive Immune Response
• Primary response• Secondary response• Humoral immunity:– B cells, plasma cells, antibodies: target
extracellular pathogens• Cell-mediated immunity– T cells, dendritic cells – antigen is inside a cell
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Overview of the Adaptive Immune Response
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Anatomy of the Lymphoid System
• Lymphatic Vessels• Secondary lymphoid Organs• Primary Lymphoid Organs
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Lymphocytes are responsible for the specific immune response
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What promotes an immune response?
• Antigens– Usually proteins or polysaccharides– Foreign substance with MW of 10,000 daltons– Examples of microbial antigens: bacterial capsules,
cell walls, flagella, toxins of bacteria
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Antibodies bind antigens
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Some molecules are not recognized as antigens until bound to another
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How are antigens recognized?
• Self markers also known as MHC markers• MHC (major histocompatibility complex)• MHC Class I-produced by all body cells• MHC Class II-produced by B cells, T cells, and
antigen presenting cells
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Structure of an antibody
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5 classes of antibodies
IgMProduced 1st
Complement activationPrimary function =
neutralize pathogens in the bloodstream
10 antigen binding sites
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5 classes of antibodies
IgGLongest half-lifeSmall enough to
cross endothelium bbb, some types of placenta
Main antibody produced in 2° immune reactions
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5 classes of antibodiesIgAMonomeric & dimeric
Dimer = secretory IgAsIgA = most abundant AbSecreted across mucosal surfaces
in mucus & many other secretions (tears, saliva, milk)
Binding → neutralize toxins, block viral and bacterial attachment
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5 classes of antibodies
IgEBound to Fc region of
mast cells and basophils
Cross-linking of IgE by antigen → degranulation
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5 classes of antibodies
IgDActivation of
basophils & mast cells
Activation of B cellsHighly conservedFunctions minimally
elucidated
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What can happen when antibody binds antigen?
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How are B cells activated?
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B cell activation by Helper T cell
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Primary and secondary response to antigen
•Affinity maturation• Class switching IgM → IgG IgM → IgA
Memory B cells+ memory helper T cells: long lived (years)
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Helper T cells help activate other immune cells
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T cells• Have own T cell receptor (TCR)• Do not make antibodies• Must recognize MHC markers which
“present” antigen
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MHC markers
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Cytotoxic T cells recognize MHC Class I markers
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Helper T cells recognize MHC Class II
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Dendritic cells can activate T cells
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Cytotoxic T cells
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Cytotoxic T cells
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Cytotoxic T cells identify infected body cells
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Helper T cells activate macrophages
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Helper T cells activate B cells
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T cell-independent antigens
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Antibody-dependent cell-mediated cytotoxicity
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