Transcript Lecture 5 T Cell-Mediated Immunity

Lecture 16
Cellular Cooperation and Antigen
Recognition
Cellular Cooperation
antigen
TH
B
Antigen presentation to T
and B cells by APC
Antigen presenting cell
T cells elaborate cytokines to
facilitate B cell proliferation
and maturation
Plasma Cells
Antibody secretion by
plasma cells
Antigen Presenting Cells
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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)
Types of Professional Antigen
Presenting Cells
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Macrophages/monocytes
Dendritic cells (e.g.., Langerhan’s cells)
B cells
Properties of
Professional
AntigenPresenting
Cells
Cellular Cooperation and
Antigen Recognition
+
APC
Extracellular
Antigen
Class II
MHCassociated
antigen
CD4+ Helper T
Lymphocyte
The Role of Adjuvants
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Depot effect
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Macrophage activation
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antigen persists for long period
resistance to rapid degradation
production of non-specific enhancing factors
Non-specific T cell signal
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provides "second" signal to B cell normally
provided by T cell
Types of Adjuvants
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Freund's Complete Adjuvant (Water-in-oil emulsion)
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Aluminum Hydroxide Gel
Microbial Adjuvants
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mineral oil
emulsifying agent
microbial preparation (eg. heat-killed extract of Mycobacterium
tuberculosis)
aqueous phase containing antigen
C. parvum
BCG
Peptides and Synthetic Polymers
Effector Mechanisms
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Mechanisms that are used by the immune system to eliminate
pathogens (or other substances) from the body
Cellular effector mechanisms
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Activated T cells
Natural killer cells
Humoral effector mechanisms (antibody)
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Neutralization
Opsonization
Complement activation
Antibody-dependent cell-mediated cytotoxicity (ADCC)
Effector Activity Against Pathogens
Cytokines
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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.
Lymphocyte Migration, Activation, and Effector
Function Depends on Cell-Adhesion Molecules
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A variety of cell surface polypeptides serve as
receptors to ensure appropriate cell-cell
interactions. These polypeptide include:
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Selectins
Integrins
Immunoglobulin Superfamily
Mucin-like Vascular Addressins
T-cell Mediated Cytotoxicity
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Necrosis
Programmed cell death or apoptosis
Summary
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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