Lymph node stromal cells constrain immunity via MHC class II self-antigen presentation

Area of Science:

• Immunology
• Cell Biology
• Transplantation Immunology

Background:

• Lymph node stromal cells (LNSCs) are crucial for T cell regulation.
• LNSCs induce deletion of self-reactive CD8+ T cells via MHC-I and anergy of CD4+ T cells via MHC-II.
• The role of LNSC-expressed MHC-II in maintaining peripheral immune homeostasis is not fully understood.

Purpose of the Study:

• To investigate the role of MHC-II expression on LNSCs in regulatory T cell (Treg) homeostasis and immune quiescence.
• To determine the impact of LNSC MHC-II deficiency on T cell activation and transplant outcomes.

Main Methods:

• Utilized lymph node transplantation models with manipulated MHC-II expression on stromal cells.
• Analyzed T cell populations (CD4+, CD8+, Tregs) for activation and proliferation markers.
• Assessed immune responses and transplant rejection dynamics.

Main Results:

• MHC-II expression on LNSCs is essential for the homeostatic maintenance of Tregs.
• Absence of LNSC MHC-II leads to activation of both CD4+ and CD8+ T cells.
• LNSC MHC-II presentation of self-antigens supports non-proliferative Treg maintenance and limits T cell immunity, preventing transplant rejection.

Conclusions:

• LNSC MHC-II plays a critical role beyond T cell anergy, actively maintaining Treg populations.
• LNSC MHC-II is vital for immune quiescence and preventing spontaneous T cell activation.
• This study uncovers a novel mechanism of peripheral immune regulation mediated by LNSCs.