FABP5 regulates ether lipid metabolism to ameliorate atopic dermatitis.

Atopic dermatitis is an allergic skin disease associated with a profound reorganization of the epidermal lipidome. The effect of the altered lipidome on the skin-resident immune cells that drive disease is unclear. Previous reports identified Fatty acid binding protein 5 (FABP5) as a biomarker for atopic dermatitis, yet how FABP5 might contribute to disease pathogenesis is unknown. Here, we use a murine model of atopic dermatitis, to demonstrate that FABP5 is highly expressed in immune and epithelial cell lineages and that FABP5 protects against skin inflammation. Lipidomic analysis revealed that FABP5 deficiency broadly disrupts the systemic abundance of ether-linked lipids, a minor but important subset of glycerophospholipids. We show that these changes in ether lipid abundance are crucial for the proper regulation of platelet activating factor (PAF), a potent inflammatory ether lipid derivative. Concordantly, we observe elevated PAF in FABP5-deficient mice with dermatitis and that depletion of basophils, a major source of PAF, is sufficient to ameliorate disease in these animals. Altogether, our findings reveal a novel role for FABP5 in the control of allergic inflammation through the modulation of ether lipid and PAF metabolism.