The Epstein-Barr virus-induced gene 2–Cholesterol 25-hydroxylase axis is essential for the recruitment of mast cell progenitors.

Introduction/Rationale: Basophils, eosinophils, and mast cells (MCs) are granulocytes that expand in the airways during type 2 inflammation (T2I)-associated diseases, where they are thought to play a major role in disease pathobiology. While the chemotactic signals recruiting basophils and eosinophils to inflamed tissues are well characterized, the signals directing MC progenitor (MCp) recruitment remain unknown.

Methods: We conducted single-cell RNA sequencing on flow-sorted MCps and pulmonary endothelial cells, cross-referencing MCp chemokine receptor and endothelial ligand expression to define a series of candidate signals. In addition, we adapted an approach in which mice were intravenously injected with FITC-labeled anti-CD45 to distinguish immune cells within the vasculature from those within the lung parenchyma, thereby tracking the dynamics of MCp recruitment following HDM challenge.

Results: Mouse MCps displayed high expression of Gpr183, encoding the Epstein-Barr virus-induced gene 2 (EBI2), while pulmonary endothelial cells highly expressed cholesterol 25-hydroxylase (Ch25h), the enzyme responsible for generating EBI2 ligands. These transcriptional profiles were validated in publicly available human scRNA-seq datasets. In wild-type mice, MCps rapidly entered and matured within the lung parenchyma following allergen exposure. In contrast, MCp recruitment to the lung parenchyma was abolished in both Vav1Cre; EBI2FL/FL (Mice with hematopoietic cell–specific deletion of EBI2) mice and Ch25h-/- mice.

Conclusion: Our findings suggest a key role for the EBI2-Ch25h axis in directing MCp recruitment during T2I.