TH9 cells are required for tissue mast cell accumulation during allergic inflammation

Area of Science:

• Immunology
• Allergic Inflammation Research
• Cell Biology

Background:

• Interleukin-9 (IL-9) is crucial for mast cell growth and survival.
• While various cells produce IL-9, the specific cells mediating mast cell accumulation in allergic inflammation are not fully understood.

Purpose of the Study:

• To investigate the role of T helper 9 (TH9) cells in mast cell accumulation within allergic lung inflammation models.
• To determine if TH9 cells are a significant source of IL-9 driving this process.

Main Methods:

• Adoptive transfer of ovalbumin-specific TH2 and TH9 cells into recipient mice.
• Assessment of mast cell accumulation and protease expression in wild-type and PU.1-deficient T cell mice.
• Analysis of IL-9 levels and mast cell infiltration in Rag1(-/-) mice.

Main Results:

• TH9 cell recipients showed significantly increased mast cell accumulation and protease expression compared to TH2 recipients.
• Mast cell accumulation was dependent on IL-9, not IL-13.
• Reduced IL-9 in PU.1-deficient T cells correlated with diminished mast cell numbers and protease expression, indicating a TH cell-dependent mechanism.
• Rag1(-/-) mice exhibited reduced mast cell infiltration, underscoring the role of T cell-derived IL-9.

Conclusions:

• TH9 cells are a primary source of IL-9 in allergic inflammation models.
• TH9 cells play a critical role in mast cell accumulation and activation during allergic responses.