T-Cell Activation and Effector Mechanisms Flashcards
What are the two types of TCRs? Which is most common (95% of T cells have it)
- Alpha-beta - most common
- Gamma-delta
Do alpha-beta TCRs recognize the peptide, the MHC molecule, both, or neither?
Both
What four proteins make up the CD3 complex?
Gamma, delta, epsilon, zeta
What co-receptor do CTLs express?
CD8
What co-receptor do Th cells express?
CD4
What proteins are used as costimulation to activate naive T cells? What do they bind to?
B7 proteins on activated dendritic cells
Bind to CD28 TCRs on cell surface
What growth factor/cytokine can helper T cells supply killer T cells, allowing the CTLs to proliferate?
IL-2
What provides co-stimulation for B cell activation?
A helper T cell through CD40L
What pattern recognition receptor on dendritic cells sense LPS?
TLR 4
What cytokine do dendritic cells produce in lymph nodes when they have been activated by macrophages and other cells? What cell does this cytokine help activate?
IL-12 - this helps activate virgin Th cells (Th1)
What cytokines do Th1 cells produce? What do they do?
- TNF: activates macrophages and NKCs
- IFN-γ: influences class switching in B cells
- IL-2: recharges NKCs and stimulates growth of CTL’s and Th1 cells as well
What cytokines do Th2 cells produce? What do they do?
- IL-4: stimulates proliferation of Th cells, B cell growth, production of IgE Abs
- IL-5: stimulates B cell production of IgA
- IL-3: stimulates production of mucus in GI system
What type of infection are Th17 helper cells useful in?
Fungal infections
What are Th0 helper cells?
“Unbiased” cells - dendritic cells tell them where to go, but not how to differentiate - they do so based on the cytokine environment they travel to
What cytokine do Th1 and Th2 cells produce to provide negative feedback on each other?
Th1 cells make IFN-γ to decrease Th2 cell production
Th2 cells produce IL-10 to reduce Th1 cell production
What type of Th and B cells do Peyer’s patches produce?
Th2 helper cells
B cells that secrete IgA Abs
Explain how the tuberculin (PPD) test works.
If you’ve been infected with Tb or have it, memory Th1 cells recognize tuberculin fragments presented by DC’s under the skin. These Th1 cells secrete IFN-γ and TNF which activate tissue macrophages, recruit neutrophils, cause redness and swelling - positive TB test. You have to wait a few days so memory Th cells can be reactivated.
What are the two ways CTLs kill cells?
- Perforin - binds to membranes, drills holes and Granzyme B - triggers apoptosis cascade
- Surface protein - FasL - binds to Fas on target’s surface –> apoptosis
What type of Th and B cells will lymph nodes produce after a skin puncture?
Th1 cells
B cells secreting IgG Abs
