Adaptive Immunity II Flashcards
Where does antigen recognition by a naive T cell take place?
In secondary lymphoid organs following antigen presentation
What drives the activation of antigen-specific T cells and the clonal expansion of the population?
the autocrine and paracrine action of IL-2
Where do memory or infected cells go after they leave the lymphoid organ?
They migrate to the infected tissue
Once the antigen/pathogen has been cleared the cells will then die via apoptosis
What are the three signals required for optimal T-Cell activation and proliferation?
- Signal 1= antigen-specific TCR engagement (MHC I and MHC II)
- Signal 2= contact with co-stimulatory ligands
- Signal 3= cytokines directing T-cell differentiation into distinct effector cell types
What is the co-stimulatory receptor that helps to facilitate activation?
CD28
What is the negative co-stimulatory receptor that helps to turn the activation off?
CTLA-4 (CD152)
How does CTLA-4 (CD152) work?
It is induced within 24 hours after activation (peaks 2-3 days post stimulation)
What are the 5 distinct subset pathways T cells can enter after activation?
- TH1 and TH2
- TH17
- TREG
- TFH
What are the two things that signals 1 and 2 induce in T cells?
- Up-Regulation of Pro-Survival genes
- Transcription of IL-2 AND IL-2R genes
What is the difference between central memory cells and effector memory cells?
Central Memory Cells
* reside in/travel between secondary lymphoid tissues
* Live longer/divide more times than TEM cells
* Are rapidly reactivated by second Ag exposure
* Can differentiate into several subset types depending on cytokine environment
Effector Memory Cells
* Travel to/between tertiary tissues
* Contribute better to first-line defenses
* Rapidly re-acquire effector functions on second Ag exposure
What are the two B cell responses elicited by distinct antigen types?
- T-Cell dependent response
- T-Cell independent response
When are T-Cell dependent responses usually generated?
Upon recognition of the protein Ag
When are T-Cell independent responses usually generated?
Upon exposure to multivalent/ polymerised Ag
What is somatic hypermutation?
somatic hypermutation is a process that introduces random mutations into the variable regions of the immunoglobulin genes
(the genes that encode B Cell antibodies)
- occurs in the germinal centres
What is Class Switching?
Class switching is a process that occurs in mature B cells, where the constant region (or isotype) of the antibody molecule is changed without altering the specificity for the antigen.
