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The second touch hypothesis: T cell activation, homing and polarization.
1Division of Inflammation Biology, La Jolla Institute for Allergy & Immunology, La Jolla, CA 92037, USA.
F1000Research
|January 15, 2015
Summary
The second touch hypothesis proposes sequential T cell activation and polarization, requiring antigen presentation in peripheral tissues for full differentiation. This highlights the critical role of non-lymphoid antigen presentation for experienced T cells.
Area of Science:
- Immunology
- Cell Biology
Background:
- T cell activation, proliferation, and polarization are key immune responses.
- The 'second touch' hypothesis suggests these events are sequential and context-dependent.
Purpose of the Study:
- To present a conceptual framework on the significance of peripheral antigen presentation to antigen-experienced T cells.
- To elaborate on the 'second touch' hypothesis regarding T cell differentiation.
Main Methods:
- Conceptual framework development.
- Review of existing immunological principles of T cell activation and differentiation.
Main Results:
- T cell activation and homing receptor induction occur in peripheral lymph nodes upon initial antigen encounter.
- Full T cell polarization and differentiation into specific T helper lineages (Th1, Th2, Th17, iTreg) require a second antigen presentation event in non-lymphoid tissues.
Conclusions:
- Peripheral, non-lymphoid antigen presentation is crucial for the complete functional polarization of antigen-experienced T cells.
- The 'second touch' hypothesis provides a framework for understanding T cell differentiation in inflammatory settings.
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