Sublingual immunotherapy using peach extract enriched in Pru p 3 (Pru p 3‐enriched‐SLIT) brings a new perspective to treating patients with allergy to lipid transfer proteins. We evaluate the immunological changes induced by Pru p 3‐enriched‐SLIT during one year.

Three groups are included: peach allergic patients who receive Pru p 3‐enriched‐SLIT, peach allergic untreated patients, and controls. Peripheral blood mononuclear cells are obtained before treatment and at different time‐points. Monocyte‐derived dendritic cells (moDCs) maturation and lymphocyte proliferation are assessed by flow cytometry. Data showed a significant reduction of moDCs maturation status during one year of treatment and an increase in PD‐L1. Moreover, we observed a significant decrease of the Pru p 3‐specific proliferation of effector cells and an increase in regulatory T (Treg) cells with higher PD‐L1 expression and IL‐10 production. These are observed in patients treated only.

Successful Pru p 3‐enriched‐SLIT is linked to an important immunosuppression of allergen‐specific effector T cells, potentially due to an increase of allergen‐specific Treg cells. These cellular changes are orchestrated by the activity of moDCs promoting the expression of PD‐L1 that will participate in the regulatory response. These changes may serve as biomarkers during SLIT alongside other features such as IgE/IgG₄ ratio.