Intestinal mast cell-derived leukotrienes mediate the anaphylactic response to ingested antigens
Anaphylaxis is a life-threatening complication of allergen exposure. While mechanisms governing anaphylaxis after intravenous injection have been defined in mice, these models neglect mucosal exposure that accompanies food ingestion. We investigated the role of mast cell populations within the intestine of mice in response to antigens delivered orally. Oral anaphylaxis required IgE-FceR1 signaling, and profiling of intestinal mast cells revealed a rapidly developing population shaped by epithelial cues. Intestinal mast cells were largely epithelium-resident and displayed divergent transcriptomes and effector functions from connective tissue mast cells found throughout the body. Histamine synthesis was diminished and leukotriene generation enhanced. Mice genetically deficient in cysteinyl leukotriene synthesis, or those treated with aLOX5 antagonist, Zileuton, were protected from oral anaphylaxis whereas that elicited by intravenous injection was unaltered. Overall design: BALB/cJ female mice were sensitized subcutaneously with  5ug endograde OVA + 1mg aluminum hydroxide in 200ul PBS on d0 and d7 under ketamine/xylazine treatment. Mice were then challenged intragastrically with 50mg of OVA (Sigma grade III) in 200ul PBS starting on day 14. These mice were challenged every other day, 5 times in total, by oral gavage.  5 days after the 5th OVA challenge, MCs were sorted via FACS Aria for scRNAseq analysis.