Intestinal mast cell–derived leukotrienes mediate the anaphylactic response to ingested antigens

Anaphylaxis is a life-threatening complication of food allergen exposure. Although mechanisms governing anaphylaxis after intravenous injection are defined in mice, these models neglect mucosal exposure that accompanies ingestion. We investigated the role of mast cells within the intestine of mice and found that oral anaphylaxis required immunoglobulin E–Fcε receptor 1 (IgE-FcεR1) signaling. Intestinal mast cells were a heterogeneous population, shaped by epithelial cues. Compared with connective tissue mast cells found throughout the body, intestinal mast cells largely resided in the epithelium, displayed divergent transcriptomes and effector functions, and had a diminished ability to generate histamine, but they enhanced leukotriene synthesis. Mice genetically deficient in cysteinyl leukotriene synthesis, or those treated with the arachidonate 5-lipoxygenase (aLOX5) antagonist zileuton, were protected from oral antigen–induced responses, whereas those elicited by intravenous injection were unaltered.