Molecular and cellular mechanisms in food anaphylaxis

摘要 食物过敏是由IgE抗体与肥大细胞（MC）结合的抗原交联介导的，并且通常是由免疫球蛋白引起的。 与肠道生态失调有关IgE对食物的致敏性本身不足以引起食物过敏反应。 肠道MC负荷，控制肠道通透性和全身抗原吸收，是一个重要的 行列式鸟嘌呤核苷酸交换因子DOCK 8对STAT 3激活、IL-22和IL-10的表达具有重要作用。 17生产由于食物过敏和过敏反应是DOCK 8缺陷患者的主要特征，因此DOCK 8 缺乏提供了一个有吸引力的疾病模型，以确定潜在的食物过敏的机制。 我们发现DOCK 8缺陷患者血清类胰蛋白酶水平升高。Dock 8-/-小鼠表现出过度的IgE- 介导的过敏反应，口服，但不是腹腔抗原的挑战，以及肠道MC扩张，我们表明， 不是MC内细胞固有DOCK 8缺陷的结果，也不依赖于IgE。小鼠 在T细胞表型复制Dock 8-/-小鼠中DOCK 8的选择性缺陷，并且两者都表现出类似的肠道生态失调T细胞 Dock 8-/-小鼠的小肠（SI）固有层（LP）中的细胞具有降低的IL 22和IL 17表达 IL 4和IL 13表达增加。DOCK 8缺陷型SI上皮细胞表达减少， 抗菌肽（AMP）基因，但增加了簇细胞的数量和IL 25的表达升高。治疗 与sIL-22或口服抗生素鸡尾酒使肠道MC扩张正常化，这表明了对 由17型细胞因子缺乏驱动的生态失调。IL-25和IL-4阻断可降低肠MC负荷和被动 Dock 8-/-小鼠的口服过敏反应，表明IL-25的关键作用，它促进2型细胞因子的产生 ILC 2和Th 2细胞，以及作用于MC的IL-4。重要的是，无菌（GF）WT接受者的粪便中 来自常规饲养的Dock 8-/-小鼠的微生物群移植（FMT）具有显著更大的肠 MC负荷与来自常规提高的WT对照的FMT的GF WT接受者相比。因此，我们建议 研究调查了DOCK 8缺乏的微生态失调可能增加肠道MC负荷的机制 从而促进过敏反应与典型食物过敏患者有关。 我们将检验以下假设：1）由于缺陷的细胞因子， D 0 CK 8缺陷中的STAT 3激活导致肠道生态失调，2）生态失调导致肠簇 细胞产生IL-25，其驱动ILC 2和Th 2细胞产生2型细胞因子，和3）IL-4， 反过来，驱动肠道MC扩张和活化，从而促进对摄入抗原的过敏反应。 我们将利用转基因小鼠，并利用我们对DOCK 8缺陷患者的访问， 先前已充分表征的典型食物过敏儿童的粪便样本，以测试我们的假设。 拟议中的研究将阐明免疫机制如何对维持肠道免疫至关重要。 微生物组调节肠道MC扩张和激活，从而调节食物过敏的严重程度， 确定预防和治疗食物过敏的新策略。

Abstract Food allergy is mediated by antigen crosslinking of IgE antibodies bound to mast cells (MC) and is often associated with intestinal dysbiosis. IgE sensitization to food is not by itself sufficient to drive food anaphylaxis. Intestinal MC load, which controls intestinal permeability and systemic antigen absorption, is an important determinant. The guanine nucleotide exchange factor, DOCK8, is important for STAT3 activation, IL-22, and IL- 17 production. As food allergy and anaphylaxis are cardinal features of DOCK8 deficient patients, DOCK8 deficiency offers an attractive disease model for identifying mechanisms underlying food allergy. We find elevated serum tryptase levels in DOCK8 deficient patients. Dock8-/- mice exhibit exaggerated IgE- mediated anaphylaxis to oral, but not i.p. antigen challenge, as well as intestinal MC expansion, which we show is neither a consequence of a cell intrinsic DOCK8 deficiency within MCs, nor dependent on IgE. Mice with selective deficiency in DOCK8 in T cells phenocopy Dock8-/- mice, and both exhibit similar intestinal dysbiosis T cells in the small intestine (SI) lamina propria (LP) of Dock8-/- mice have decreased expression of Il22 and Il17 and increased expression of Il4 and Il13. DOCK8 deficient SI epithelium has decreased expression of antimicrobial peptide (AMP) genes, but increased numbers of tuft cells and elevated Il25 expression. Treatment with either sIL-22 or an oral antibiotic cocktail normalizes intestinal MC expansion, suggesting a critical role for dysbiosis driven by type 17 cytokine deficiency. IL-25 and IL-4 blockade reduce intestinal MC load and passive oral anaphylaxis in Dock8-/- mice, suggesting a critical role for IL-25, which promotes type 2 cytokine production by ILC2s and Th2 cells, and for IL-4, which acts on MCs. Importantly, germ free (GF) WT recipients of fecal microbiota transplantation (FMT) from conventionally raised Dock8-/- mice have significantly greater intestinal MC load compared to GF WT recipients of FMT from conventionally raised WT controls. Thus, our proposed studies investigate the mechanisms by which dysbiosis in DOCK8 deficiency may increase intestinal MC load and thereby promote anaphylaxis are relevant to patients with classic food allergy. We will test the hypotheses that 1) reduced production of type 17 cytokines due to defective STAT3 activation in DOCK8 deficiency results in intestinal dysbiosis, 2) dysbiosis causes intestinal tuft cells to produce IL-25, which drives type 2 cytokine production by ILC2s and Th2 cells, and 3) IL-4, in turn, drives intestinal MC expansion and activation, thereby promoting anaphylaxis to ingested antigen. We will make use of transgenic mice and take advantage of our access to DOCK8 deficient patients and previously well-characterized fecal samples from children with classic food allergy to test our hypotheses. The proposed studies will delineate how immune mechanisms important for maintaining the intestinal microbiome regulate intestinal MC expansion and activation, and thereby the severity of food allergy, thus identifying novel strategies for the prevention and treatment of food allergy.