Review Initial differentiation s thymic maturation Initial differentiation

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Review…

Review…

Initial differentiation… ='s “thymic maturation”

Initial differentiation… ='s “thymic maturation”

Initial differentiation… c-Kit (receptor for stem cell growth factor) CD 44 (an adhesion molecule)

Initial differentiation… c-Kit (receptor for stem cell growth factor) CD 44 (an adhesion molecule) CD 25 ( chain of IL-2 receptor)

Fundamental notion: Positive selection of thymocytes bearing receptors capable of binding self-MHC molecules which

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 selftolerance.

Another fundamental notion… There are first “double negatives” (DN’s)… Then there are “double positives”

Another fundamental notion… There are first “double negatives” (DN’s)… Then there are “double positives” (DP’s)…. DN and DP refer to the presence of CD 4 and CD 8

The effect Note what’s happening and where

The effect Note what’s happening and where

Evidence for Positive selection & Negative selection

Evidence for Positive selection & Negative selection

Activation… in the periphery… some key events:

Activation… in the periphery… some key events:

“Overview” (!)

“Overview” (!)

Some common themes in signal transduction… • The involvement of receptors • The generation

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

The co-stimulatory signal

The co-stimulatory signal

Co-Stimulatory Differences among Antigen Presenting Cells (APC’s)

Co-Stimulatory Differences among Antigen Presenting Cells (APC’s)