Prolonged T cell - DC macro-clustering within lymph node microenvironments initiates Th2 cell differentiation in a...

Area of Science:

• Immunology
• Cellular Biology
• Dermatology

Background:

• T helper 2 (Th2) immune responses are crucial for allergic reactions but their in vivo generation is not fully understood.
• Existing models suggest low-grade T cell stimulation, but large-scale Th2 generation mechanisms remain unclear.

Approach:

• Quantitative imaging was employed to visualize early Th2 differentiation within lymph nodes (LNs) after cutaneous allergen exposure.
• T cell activation, integrin-dependent macro-clustering at the T-B border, and clustering behavior during Th1 differentiation were analyzed.
• The influence of skin sensitization site on Th2 macro-cluster formation was investigated.

Key Points:

• Th2 differentiation involves enhanced T cell activation and extensive integrin-dependent macro-clustering, distinct from Th1 responses.
• Th2 macro-cluster formation is unexpectedly dependent on the skin sensitization site.
• Divergent activation states of migratory cDC2 from different dermal tissues drive these site-specific differences.

Conclusions:

• Enhanced costimulatory molecule expression by cDC2 promotes T cell macro-clustering and cytokine sensing, initiating Th2 responses.
• Dedicated priming micro-environments are generated in a skin site-specific manner to initiate Th2 responses in vivo.
• These findings challenge current models and highlight the importance of the sensitization site in shaping adaptive immunity.