BACKGROUND: Omalizumab (XOLAIR®)-assisted multi-food oral immunotherapy (mOIT) has been shown to safely, effectively, and rapidly desensitize patients with multiple food allergies. In our clinical trial (NCT02626611) on omalizumab-assisted mOIT, different desensitization outcomes (success or failure of desensitization) were observed following a period of either continued or discontinued mOIT. However, the association between the immunological changes induced by omalizumab-assisted mOIT and desensitization outcomes has not yet been fully elucidated. In this study, due to the key roles of regulatory T (Treg) cells and the type 2 helper T cell (Th2) pathway in immune tolerance to food allergens, we aimed to characterize their association with the desensitization outcomes of omalizumab-assisted mOIT. METHODS: Mass cytometry and multiplex cytokine assays were performed on blood samples obtained from participants with allergies to peanut, cashew, or milk in our phase 2 clinical study (NCT02626611). Comprehensive statistical and bioinformatic analyses were conducted on high-dimensional cytometry-based single-cell data and high-throughput multiplex cytokine data. RESULTS: Our results demonstrated that the frequency of HLA-DR CONCLUSIONS: We demonstrated that the frequency of HLA-DR