T Cell Differentiation

How do T cells travel from one lymph node to another?

through efferent vesseles

WRITE DOWN DIFFERENT SUBSETS OF T CELLS

memorize blue 8-9 table

What happens after you activate CD4 cells?

gives rise to effector CD4 T cells with distinctive helper functions

What determines what kind of effector T cell is made from a naive T cell?

depends on what cytokines that they are exposed to; this will then drive a defining transcription factor which gives it its specific function

What happens if an effector T cells is exposed to different cytokines?

the T cell can become the effector cell that correlates with the new cytokines it is exposed to; plasticity in T cells (positive feedback)

What required stronger activation: CD4 or CD8 T cells?

CD8

What differentiates the two ways CD8 T cells can be recognized?

dendritic cells with some types of viruses can activate a naive T cell on their own; some viruses in dendritic cells cannot activate by itself and need some help

Describe the activation process of a CD8 T cell when the dendritic cell does not need any help

dendritic cell sends a strong signal to activate the CD8 T cell to effector status; activated virus-specific CD8 T cell makes IL-2, driving its own proliferation and differentiation

Describe the activation process of a CD8 T cell when the dendritic cell does need help

dendritic cell activates virus-specific CD4 T cell to secrete IL-2 and virus-specific CD8 T cell to express IL-2 receptors; IL-2 from the CD4 T cell drives the proliferation and differentiation of the virus-specific CD8 T cell

What cell-surface molecules are present on a CD4 T cell when it is resting?

L-selectin, LFA-1, CD2, CD4, TCR, CD44, C45RA, CD45RO

What cell-surface molecules are present on a CD4 T cell when it is activated?

VLA-4, LFA-1, CD2, CD4, TCR, CD44, CD45RO

What does L-selectin do?

binds to carbohydrates that are on the epithelial venules; important for transportation from lymph nodes into organs; binds to ICAM-1 on target cels

What is VLA-4?

very late antigen 4; allows activated T cells to leave the circulation and migrate to sites of infection; binds onto VCAM-1 on activated endothelium

What is activated endothemium?

endothelium of blood vessels at the site of infection

What is the purpose of binding of VCAM-1 to VLA-4?

will make the T cell respond to chemokines that will drive the T cell to get out of circulation and go to site of infection

What is B7?

part of co-stimulatory signal for CD8 T cells; will bind to CD28

What is the relationship between the subsets of CD4 T cells and the cytokines they produce?

the cytokines will all have some effect on the other; e.g. T-reg produces lots of cytokines that counters TH1,TH2, and TH17 cells so it can suppress their activities

Describe the process of cytokines being able to alter gene expression

cytokine receptor subunits and JAKs are all separate; cytokine receptor subunits bind JAKs, cytokine binding assembles the receptor, which is then phosphorylated; STATs bind to phosphorylated receptor and are then phosphorylated, phosphorylated STAT dimers go to the nucleus and initiate gene expression

What are JAK proteins?

janus kinases; bind to cytokine receptor

What are integrins?

forms loose interactions between T cell and target cell; displayed on Tcell surface and binds to other factors on target cell which allows TCR to scan the target cell surface to find MHC molecules

What happens when the TCR finds MHC molecules on a target cell (generally)?

TCR bidning to MHC will be strengthened by CD8; lead to integrins binding to a high affinity which will help with antigen binding; cause mobilization of lytic granules (granzyme, perforin) which will be released into target cell to kill it

How does a cytotoxic CD8 T cell kill a cell?

cytotoxic CD8 T cell recognizes virus-infected cell and programs it to die (granule release to induce apoptosis); moves onto next cell and then the next and so on

How do TH1 cells induce macrophage activation?

TH1 cell and infected macrophage come together; T cell binds to and activates macrophages (with CD40 and CD40 ligand as well as IFN-gamma and IFN-gamma receptor); killing of intravesicular bacteria

What do T follicular cells do?

recognizes a peptide derived from B cell’s antigen; naive B cell and Tfh cell exchange signals (CD40 and CD40 ligand and will upregulate cytokines) that begin process of B cell activation

What do regulatory T cells do?

suppression of autoreactive T cells by interacting with the same antigen-presenting cell