T-cells Flashcards
What protein do T-helper cells display on their surface and how do they differentiate?
All T-helper cells display CD4 on their surface and start out as ‘Th0’ precursors. Th0 cells are present in the paracortex of the lymph nodes (and other appropriate areas) and are activated by DCs. They differentiate into Th1, 17, 2, fh, or reg cells depending on the conditions and cytokines/chemokines present during activation.
What do Th1 cells do and what lymphokine (cytokine) do they produce?
These are delayed hypersensitivity T-cells, after activation they divide and the daughter cells enter the circulation. When they encounter antigen, they secrete lymphokines including Interferon-gamma (INF-g) which is pro-inflammatory and chemotactic for mono/macrophages. Monocytes attracted by INF-g become M1, ‘angry’ macrophages. Poison ivy is a stimulator of Th1. Th1 also secrete IL-2, which helps activate cytotoxic T-cells.
What do Th17 cells do and what lymphokine do they produce?
Th17 is a very pro-inflammatory T-cell, much more inflammatory than Th1. Th17 produces IL-17 which also activates M1, angry macrophages. It has a role in resisting difficult bacterial or yeast infections.
What concerns arise during Th1 and Th17 activities?
Th1 and Th17 both activate strong inflammatory reactions in an effort to get dangerous pathogens under control quickly. This can get out of control and cause significant tissue damage, especially if it becomes chronic.
What do Th2 cells do and what lymphokine do they produce?
Activated Th2 cells behave much like Th1 cells and leave the node to circulate through the blood. When Th2 cells encounter antigen, they secrete IL-4 which also attracts macrophages but activates the alternative pathway to create M2 macrophages that are more involved in healing or walling off of pathogens not killed by M1 macros. IL-4 is also chemotactic for eosinophils, which are effective against parasites.
What do Tfh cells do?
T-follicular helper cells move from the paracortex of the lymph node to the follicles, where they trigger the B cells that have recognized antigen to become activated and begin secreting antibody. Tfh secrete a variety of lymphokines and by direct contact trigger they stimulate the B cells to class switch from IgM to IgG, IgE, or IgA depending on their location in the body (gut, lungs, etc.)
What to Treg cells do and what lymphokine do the produce?
T-regulatory helper cells (~5% of all Th cells) suppress the activation and function of all other Th cells. They make the transcription factor FoxP3, and secrete TGF-b and IL-10. One Treg can suppress 1000 Th cells and does so non-specifically (any nearby Th is suppressed). Treg cells inhibit over-reaction and autoimmunity.
