T Cell Responses and Cell-Mediated Immunity Flashcards
What happens when the TCR ligates to the peptide:MHC complex?
Signal transduction occurs in the T cell and then gene activation/expression!
When a T cell recognizes an MHC molecule in the thymus and it has a low affinity interaction will this molecule be selected to survive?
Yes! This is positive selection!
If it doesn’t recognize this MHC molecule, it will die by apoptosis
When a TCR that has been positively selected now has a HIGH affinity for MHC I/MHC will it survive?
NO! Will undergo apoptosis only because it could be auto-reactive
Which type of selection is Ras MEK-ERK dependent?
Positive selection. Negative selection is not dependent
What is AIRE? What if kids don’t have AIRE?
Autoimmune regulator! It is a transcriptional regulator that allows expression of non-thymic genes that will provide peptides for MHC I and subsequent negative selection.
Could lead to autoimmune diseases
What is central tolerance?
When you remove SELF-REACTIVE T lymphocytes from primary lymphoid organs (thymus)
What is peripheral tolerance?
Peripheral tolerance is immunological tolerance developed after SELF-REACTIVE T and B cells mature and enter the periphery. These include the suppression of autoreactive cells by ‘regulatory’ T cells and the generation of hyporesponsiveness (anergy) in lymphocytes which encounter antigen in the absence of the co-stimulatory signals that accompany inflammation, or in the presence of co-inhibitory signals.
What does the T-cell produce once it is activated?
It produces autocrine growth factors like IL-2 (induces cell expansion)
-Express CD154 (CD40L –> can talk to B cells)
How do CTLs kill things?
- Lyse target cells and release granules that contain proteins that will create pores in the bad cell. Such as PERFORNIN and GRANZYMES. These things destroy the cell membrane
- Expresses Fas-L which causes apoptosis
What is the function of Th1 cells? Name the signature cytokine
Th1 CD4 cells activate macrophages to kill intracellular microbes.
Cytokine: IFN-g (Gamma interferon)
What is the function of Th2 cells? Name the signature cytokine
Th2 CD4 cells help B cells proliferate and secrete antibodies like IL-3, 4,5
Also cause production of eosinophils
Cytokine: IL-4
What is the function of Th2 cells? Name the signature cytokine
Th17 cells recruit neutrophils to the site of infection
Cytokine: IL-17
What do CD4+ Regulatory cells do?
Not helper T cells because they SUPPRESS immune responses
