S1P₁ Contributes to Endotoxin-enhanced B-Cell Functions Involved in Hypersensitivity Pneumonitis

Area of Science:

• Immunology
• Pulmonary Medicine
• Environmental Health

Background:

• Hypersensitivity pneumonitis (HP) pathogenesis is often unclear, lacking effective treatments.
• Occupational bioaerosols, including endotoxins, may drive HP persistence.
• Sphingosine-1-phosphate receptor 1 (S1P1) agonists previously showed potential in preventing B-cell reactivation in HP.

Purpose of the Study:

• To investigate the impact of endotoxins on B-cell activation in established HP.
• To determine the role of S1P1 in endotoxin-induced B-cell responses in HP.

Main Methods:

• Studied endotoxin effects on experimental HP in vivo.
• Tracked S1P1 levels on B cells using S1P1-eGFP knockin mice.
• Utilized pharmacological tools to assess S1P1's role in B-cell function.

Main Results:

• Endotoxin exposure increased neutrophil accumulation and lymphocyte CD69 expression in BAL fluid.
• Endotoxins enhanced B-cell costimulatory molecules and CD69 expression, effects blocked by an S1P1 agonist.
• S1P1 modulators reduced B-cell TNF production and T-cell cooperation capacity.

Conclusions:

• S1P1 is present on B cells in experimental HP.
• Endotoxins exacerbate HP by promoting B-cell activation via S1P1.
• S1P1 agonists represent a potential therapeutic strategy for endotoxin-driven HP.