B Cell Activation and Antibody Production

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B Cell Activation and Antibody Production

• Lecture 15

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Overview of B Cell Development,
Activation, Antibody Production
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B Cell Antigens
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B Cell Responses to Thymus-Dependent Antigens (T
Cell-Dependent Antibody Responses)
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Primary and Secondary Antibody Responses
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Phases of the Humoral Immune Response
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A T-Dependent Antigen Must Contain Both B and T
Cell Epitopes
Antigen
T Cell Epitope
B Cell Epitope
LINKED RECOGNITION
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Follicles
(B Cells)
(T Cells)
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Activation of B Cells by Antigen and Complement
1. Biochemical Signals 2. Endocytosis of Antigen
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Antigen Recognition Phase of T-Dependent
Antibody Response
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Interactions of B Cells with Helper T Cells
TEM Picture
B Cell
B Cell
T Cell
Initial Contact
T-B Conjugate
Note the broad area of membrane contact between
B and T Cells.
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Helper T Cell-Dependent Activation Of B
Lymphocytes
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B-Cell Activation by Thymus-Dependent Antigens
Cytokines
CR
Linked Recognition
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Activated B Cells (Following Interaction with TH
Cells
Extra-follicular Site
Follicle
Germinal Center
Antibody Secreting Cells
Antibodies
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Late Events in T Cell-Dependent Antibody
Responses-Germinal Center Reaction

• Affinity Maturation
• Somatic Hypermutation
• Generation of Memory B Cells

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Somatic Hypermutation and Affinity Maturation of
Antibodies
Affinity maturation is the process that leads to
increased affinity of antibodies for a particular
antigen as a result of somatic mutation in the Ig
genes followed by selective survival of B cells
producing the antibodies with the highest affinity
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Affinity Maturation in Antibody Responses
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Selection of High Affinity B Cells in Germinal
Center
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Phases of the Humoral Immune Response
to T-Dependent Antigen
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Anatomy of Humoral Immune Responses
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Antibody Isotype Switching
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Isotype Switching Under the Influence of Helper T
Cell-Derived Cytokines
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Mechanism of Ig Isotype Switching
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CD4 T Cell-Dependent Effects in Antibody
Responses

• Memory B Cell Development
• Isotype Switching
• Affinity Maturation

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Thymus-Independent Antigens
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B-Cell Activation by Thymus-Independent and
Dependent Antigens
Most TI antigens are polyvalent and induce
maximal Crosslinking of membrane Ig on B cells,
without a Need for T cell help.
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Features of Antibody Responses to T-Dependent and
T-Independent Antigens
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Antibody Response to T-Dependent Antigens

• Role of Helper T Cells
• Cytokines
• CD40/CD40L interactions
• Isotype Switching
• Switch Recombination
• Cytokines and Isotypes
• Affinity Maturation
• Somatic hypermutation
• Selection for B cells which produce High Affinity
  Antibodies
• Memory B Cells

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Antibody Effector Functions
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Effector Functions of Antibodies
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Neutralization of Microbes by Antibodies
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Neutralization of Toxins by Antibodies
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Opsonization of Microbes by Antibodies
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Antibody-Dependent Cellular Cytotoxicity (ADCC)
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Functions of Complement
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Complement-Mediated Lysis of E. coli
Alive
Killed
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Cellular Interactions in Immune Responses
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The Immune Response A Summary
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