Lecture 16 Cellular Cooperation and Antigen Recognition

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Lecture 16Cellular Cooperation and Antigen
Recognition
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Cellular Cooperation
antigen
T
B

H
Plasma Cells
Antigen presentation to T and B cells by APC T
cells elaborate cytokines to facilitate B cell
proliferation and maturation
Antibody secretion by plasma cells
Antigen presenting cell

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Antigen Presenting Cells

• Must be capable of processing antigen from
  extracellular and intracellular pathogens
• Must present processed antigen on MHC class I
  II molecules
• Must express co-stimulatory molecules (cytokines)

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Types of Professional Antigen Presenting Cells

• Macrophages/monocytes
• Dendritic cells (e.g.., Langerhans cells)
• B cells

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Properties of Professional Antigen-Presenting
Cells
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Cellular Cooperation and Antigen Recognition

Class II MHC- associated antigen
APC
Extracellular Antigen
CD4 Helper T Lymphocyte
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The Role of Adjuvants

• Depot effect
• antigen persists for long period
• resistance to rapid degradation
• Macrophage activation
• production of non-specific enhancing factors
• Non-specific T cell signal
• provides "second" signal to B cell normally
  provided by T cell

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Types of Adjuvants

• Freund's Complete Adjuvant (Water-in-oil
  emulsion)
• mineral oil
• emulsifying agent
• microbial preparation (eg. heat-killed extract
  of Mycobacterium tuberculosis)
• aqueous phase containing antigen
• Aluminum Hydroxide Gel
• Microbial Adjuvants
• C. parvum
• BCG
• Peptides and Synthetic Polymers

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Effector Mechanisms

• Mechanisms that are used by the immune system to
  eliminate pathogens (or other substances) from
  the body
• Cellular effector mechanisms
• Activated T cells
• Natural killer cells
• Humoral effector mechanisms (antibody)
• Neutralization
• Opsonization
• Complement activation
• Antibody-dependent cell-mediated cytotoxicity
  (ADCC)

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Effector Activity Against Pathogens
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Cytokines

• Polypeptides produced by a variety of cell types
  including T lymphocytes.
• Cytokine production is triggered by specific
  receptor binding and subsequent signal
  transduction pathways
• Cytokine repertoire is dependent on cell type
  triggered, receptors present on that cell type.
• Cytokines act on cells that possess receptors for
  them.

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Lymphocyte Migration, Activation, and Effector
Function Depends on Cell-Adhesion Molecules

• A variety of cell surface polypeptides serve as
  receptors to ensure appropriate cell-cell
  interactions. These polypeptide include
• Selectins
• Integrins
• Immunoglobulin Superfamily
• Mucin-like Vascular Addressins

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T-cell Mediated Cytotoxicity

• Necrosis
• Programmed cell death or apoptosis

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Summary

• Effector cells and antibodies play critical roles
  in almost all adaptive immune responses
• Antigen-presenting cells play critical role in
  processing and presenting antigen to T cells
• Cytokines are released by a variety of cell types
  and regulate a variety of biological effects
• T-cell mediated cell death is largely via
  apoptosis