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-FcεR1 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. 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.

过敏性休克（Anaphylaxis）是过敏原暴露引发的危及生命的并发症。尽管目前已在小鼠模型中阐明静脉注射过敏原后过敏性休克的发病机制，但此类模型并未涵盖进食时伴随的黏膜暴露过程。本研究针对小鼠肠道内肥大细胞群在口服抗原刺激下的作用展开探究。口服性过敏性休克依赖免疫球蛋白E-Fcε受体1（IgE-FcεR1）信号通路；对肠道肥大细胞的谱型分析显示，存在一类由上皮细胞信号调控的快速发育细胞群。肠道肥大细胞大多为上皮驻留型，与全身各处的结缔组织肥大细胞相比，其转录组与效应功能均存在显著差异。该类细胞的组胺合成能力减弱，而白三烯生成则增强。遗传敲除半胱氨酰白三烯合成通路的小鼠，或经5-脂氧合酶（aLOX5）拮抗剂齐留通（Zileuton）处理的小鼠，均可免受口服性过敏性休克的影响，但静脉注射过敏原诱导的过敏性休克则未受影响。于第0天和第7天，在氯胺酮/赛拉嗪麻醉下，向BALB/cJ雌性小鼠皮下注射200μL磷酸盐缓冲液（PBS）混合液，其中含5μg内毒素级卵清蛋白（endograde OVA）与1mg氢氧化铝，以进行致敏。自第14天起，向小鼠经口灌胃200μL含50mg SigmaⅢ级卵清蛋白（OVA）的PBS溶液，以激发免疫反应。此后每隔1天通过灌胃激发一次，共进行5次。在第5次卵清蛋白激发后的第5天，通过流式细胞分选仪（FACS Aria）分选肥大细胞（MCs），用于单细胞RNA测序（scRNAseq）分析。