Sublingual immunotherapy for 4 years increased the number of Foxp3+ Treg cells, which correlated with clinical effects

Objective At least 3 years of sublingual immunotherapy (SLIT) is required to achieve long-term clinical tolerance for allergens. However, immunological changes with more than 3 years of SLIT have not yet been elucidated in detail. The present study investigated whether the numbers of regulatory T (Treg) cells and regulatory B (Breg) cells increased with 4 years of SLIT and if these increases correlated with clinical effects for pollinosis. Methods Seven Japanese cedar pollinosis patients received SLIT in 2014 or 2015 and continued treatment until May 2019. In May 2017 and May 2019, peripheral blood mononuclear cells (PBMCs) were collected from the patients, and analyzed by flow cytometer. Results (1) The visual analogue scale (VAS) was significantly higher in 2019 than in 2017. (2) The percentages of Foxp3 + Treg cells, type 1 regulatory T (Tr1) cells, and Breg cells in PBMCs were significantly higher in 2019 than in 2017. (3) The percentage of Foxp3 + Treg cells in PBMCs positively correlated with VAS, whereas those of Tr1 cells and Breg cells did not. Conclusions These results suggest that 4 years of SLIT is needed to achieve sustained increases in Foxp3 + Treg cells, which are closely associated with the efficacy of SLIT.