Functional adaptive CD4 Foxp3 T cells develop in MHC class II-deficient mice

Area of Science:

• Immunology
• Cell Biology

Background:

• CD4 Foxp3 regulatory T (T(R)) cells are crucial for immune homeostasis.
• Conventional T(R) cell development relies on thymus-mediated selection via TCR-MHC interactions.

Purpose of the Study:

• To investigate the generation of Foxp3 T(R) cells independently of MHC class II molecules.
• To characterize the phenotype and function of MHC class II-independent T(R) cells.

Main Methods:

• Utilized MHC class II-deficient (Aalpha(-/-) B6) mice.
• Analyzed T(R) cell populations in various tissues (thymus, spleen, lymph nodes, liver).
• Assessed T(R) cell surface marker expression (CD103, CD25) and in vivo/in vitro immunosuppressive functions.

Main Results:

• MHC class II-independent CD4 Foxp3 T(R) cells were detected in secondary lymphoid and peripheral tissues, but absent in the thymus of Aalpha(-/-) B6 mice.
• These T(R) cells preferentially expressed CD103 and upregulated CD25 upon activation.
• MHC class II-independent T(R) cells effectively suppressed vaccine-induced CD8 T cell responses in vivo and naive T cell proliferation/IL-2 release in vitro.

Conclusions:

• Foxp3 T(R) cells can develop independently of MHC class II, primarily in peripheral tissues.
• These peripherally generated T(R) cells exhibit potent immunosuppressive capabilities.
• The findings reveal a novel pathway for regulatory T cell generation and function.