Objective To analyze the characteristics of type II innate lymphocytes (ILC2) and fecal metabolism in a murine model of cow's milk protein allergy (CMPA) mice through non-targeted metabolomics, and explore the core pathogenesis of CMPA.

Methods On the 7th, 14th, 21st and 28th days, 0.2 mL of β-lactoglobulin and Freund's complete adjuvant suspension were intraperitoneally injected into BALB/c female mice to construct the sensitized mice in the experimental group. Meanwhile, the mice in the control group were treated with the same amount of PBS solution. On the 30th day, the β-lactoglobulin stimulation test was conducted, and the feces and small intestinal tissues of mice were collected. ILC2 in the small intestinal intrinsic lymphocyte suspension was sorted and collected by flow cytometry, and then non-targeted metabolomics detection and bioinformatics analysis were performed on ILC2 and feces. The diagnostic performance of differentially expressed metabolites (DEMs) was analyzed by receiver operating characteristic curve (ROC), and the correlation between DEMs and Th2-type cytokines (IL-4, IL-5, IL-13) was analyzed.

Results A total of 188 DEMs and 15 enriched metabolic pathways were identified in the CMPA mice and control group. Three common lipid DEMs, namely linoleic acid, 13-HODE and sphingosine, existed in fecal samples and ILC2 cell samples. Among them, sphingosine in ILC2 was positively correlated with IL-4, IL-5 and IL-13 (P ＜ 0.05), and the correlation coefficients r were 0.6, 0.62 and 0.62, respectively. The correlation coefficients r between sphingosine and cytokines in feces were 0.83, 0.86, and 0.81, respectively (P ＜ 0.05), and the correlation was significantly enhanced.

Conclusions The significant changes occurred in the sphingolipids metabolism in the ILC2 of intestinal tissues and fecal specimens in CMPA mice, and the sphingosine was closely related to the changes in Th2-type cytokine levels.