S1P₁ deletion differentially affects TH17 and Regulatory T cells

Area of Science:

• Immunology
• Neuroimmunology
• Cell Biology

Background:

• Sphingosine-1 phosphate receptor 1 (S1P₁) is crucial for lymphocyte egress from lymphoid organs.
• Fingolimod, an S1P₁ agonist, treats multiple sclerosis (MS) but its precise effects on T helper 17 (Th17) and regulatory T (T_reg) cells are not fully understood.

Purpose of the Study:

• To investigate the role of S1P₁ signaling in the homeostasis and function of Th17 and T_reg cells.
• To elucidate the impact of S1P₁ deletion on experimental autoimmune encephalomyelitis (EAE) development and progression.

Main Methods:

• Specific deletion of S1P₁ in Th17 cells using IL-17A^Cre mice.
• Specific deletion of S1P₁ in T_reg cells using Foxp3^Cre mice.
• Assessment of EAE susceptibility and T cell phenotypes.

Main Results:

• S1P₁ deletion in Th17 cells protected against EAE.
• Permanent S1P₁ deletion in T_reg cells led to autoimmunity, while acute deletion increased EAE susceptibility.
• S1P₁ deficiency altered T_reg cell distribution, phenotype, and promoted apoptosis, converting them to effector T_reg cells.

Conclusions:

• S1P₁ signaling is vital for T_reg cell homeostasis, tissue distribution, and maintaining immune tolerance.
• Long-term fingolimod therapy may impact Th17/T_reg cell balance and immune health in MS patients.
• Understanding S1P₁'s role offers insights into MS pathogenesis and therapeutic strategies.