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Activation-induced nonresponsiveness: a Th-dependent regulatory checkpoint in the CTL response
Ee Loon Tham1, Protul Shrikant, Matthew F Mescher
1Center for Immunology, Department of Biochemistry, University of Minnesota, Minneapolis, MN 55455, USA.
Journal of Immunology (Baltimore, Md. : 1950)
|January 22, 2002
Summary
CD8 T cells become activation-induced nonresponsive (AINR) but can be revived with IL-2. This process rewires T cell signaling, enabling sustained responses to antigens without CD4 T cell help.
Area of Science:
- Immunology
- Cellular Biology
- T cell activation
Background:
- CD8 T cells initially proliferate via autocrine IL-2 signaling.
- Proliferation halts within days, leading to activation-induced nonresponsiveness (AINR) and split anergy.
- AINR CD8 T cells can kill targets and secrete IFN-gamma but not IL-2.
Purpose of the Study:
- To investigate the mechanisms of CD8 T cell activation-induced nonresponsiveness (AINR).
- To explore the role of IL-2 in reversing AINR and restoring T cell function.
- To understand the signaling 'rewiring' that occurs in AINR CD8 T cells.
Main Methods:
- Analysis of CD8 T cell proliferation and cytokine production.
- Investigation of mitogen-activated protein kinase (MAPK) and IL-2 mRNA regulation.
- Assessment of T cell receptor (TCR) and costimulatory molecule signaling.
Main Results:
- AINR CD8 T cells exhibit impaired MAPK and IL-2 mRNA upregulation upon TCR/costimulation.
- Exogenous IL-2 rescues proliferation and reverses nonresponsiveness.
- AINR cells undergo signaling 'rewiring', becoming costimulation-independent for TCR-mediated IL-2 mRNA and MAPK induction.
Conclusions:
- AINR is a regulatory checkpoint in CD8 T cell differentiation, transitioning from helper-independent to helper-dependent responses.
- IL-2 acts as a critical signal to overcome this checkpoint.
- Upon IL-2 rescue, CD8 T cells can mount prolonged, costimulation-independent responses to persistent antigens.