Review

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Review
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Initial differen-tiation's thymic
matura-tion
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Initial differen-tiationc-Kit (receptor for
stem cell growth factor)CD44(an adhesion
molecule)CD25 (? chain of IL-2 receptor)
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Fundamental notion

• Positive selection of thymocytes bearing
  receptors capable of binding self-MHC molecules
  which results in MHC restriction.

• Negative selection by elimination of thymocytes
  bearing high-affinity receptors for self-MHC
  molecules alone or self-antigen presented by
  self-MHC, which results in self-tolerance.

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Another fundamental notion

• There are first double negatives (DNs)

• Then there are double positives (DPs).

DN and DP refer to the presence of CD4 and CD8
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The effect
Note whats happening and where
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Evidence for Positive selection
Negative selection
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Activation

• in the periphery
• some key events

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Overview (!)
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Some common themes in signal transduction

• The involvement of receptors
• The generation of second messengers
• The action of protein kinases and phosphatases
• The induced assembly of critical components of a
  signal transduction pathway
• Cascades
• The involvement of large and small G proteins
• The default setting for signal transduction is OFF

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The co-stimulatory signal
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Co-Stimulatory Differences among Antigen
Presenting Cells (APCs)