12- Helper T Cells Flashcards
Describe the structure of TCR complex
The TCR is a heterodimer consisting of an alpha-chain and a beta-chain. There are 4 domains:
- Variable (V)
- Constant (C)
- Transmembrane domain
- cytoplasmic domain
Located between the alpha and beta chains lies an antigen binding groove
Explain the differences in TCR complex of a helper T cell and a cytotoxic T cell.
The only difference between the TH cell and CTC complexes is the MHC class type and the CD molecule.
- TH cells have MHC class II and CD4+
- CTC have MHC I and CD8+
Explain how T cell-APC interaction results in an activation or inactivation of T cell response
When MHC presents an antigen to a TCR, the binding then causes a cascade beginning with the CD154 on the T cell binding to CD40 on the APC. These act on TCRs CD28 and APC receptor CD80/86 to cause the T cell to activate, increasing IL-2 causing T cell differentiation. Roughly 72 hours after the activation of CD28 and CD 80/86, they will cause the TCR CD152 and APC 80/86 to bind and cause inactivation of the T cell, leading to IDO release, which destroys tryptophan, which in the end leads to T cell termination
Explain the importance of co-stimulation in T cell activation
During T cell activation, two signals are required. The first is the MHC with the TCR. The second signal that is necessary to ensure T cell activation is a co-stimulation between the APC and the T cell. This signal is the binding of B7/CD80 receptor to the CD28 receptor. This will cause T cell activation and ultimately lead to release of IL-2 and T cell proliferation and differentiation. The absence of this co-stimulation will result in no response or tolerance
What is the tole of TH1 cells in the immune response to various microbes
TH1 cells release IFN-gamma that binds to the macrophage leading to the killing of phagocytosed bacteria/intracellular pathogens
What is the role of TH2 cells in the immune systems response to different microbes
TH2 cells release IL-5 which activate eosinophils that then lead to the killing of parasites
What is the role of TH17 cells in the immune systems response to different microbes
TH17 cells release IL-17 and IL-22 act on neutrophils leading to killing/destruction of fungi and extracellular pathogens
TH2 cells secrete which interleukins? What type of responses to they promote?
IL-4, IL-13, and IL-10
They generally promote antibody responses
TH17 cell development is stimulated by what? Then what do they secrete?
Stimulated by IL-6, TFG-beta, and IL-23
-they secrete IL-17 and promote neutrophil-mediated inflammation
