Effects of allergen-specific immunotherapy on functions of helper and regulatory T cells in patients with seasonal allergic rhinitis.

BACKGROUND: Seasonal allergic rhinitis (SAR) is characterized by a helper T (Th)2 cell-mediated immune response at the target site. There is a relative Th1 and/or regulatory T (Treg) cell insufficiency in patients with SAR. It has been demonstrated that there is a change in the balance between these cells after allergen-specific immunotherapy (SIT), which is a curative treatment modality for this disease. However, there are few studies that evaluate the number and function of these cells in the inflammatory area after SIT treatment.
OBJECTIVE: We aimed to investigate the distribution of Th1, Th2 and Treg cells in nasal biopsies and lavage fluid (NLF) specimens from patients with SAR, before and after SIT.
METHODS: Twenty-four, symptomatic SAR patients sensitized to Olea europeae, were enrolled in the study prior to treatment. Fifteen, non-allergic subjects with nasal septum deviation, who needed surgical treatment, served as the control group. NLF and inferior turbinate biopsies were obtained from both groups during the pollen season. Conventional, subcutaneous SIT with Olea europeae extract was initiated in patients with SAR. One year after the first biopsy, biopsies and NLF specimens were again obtained for reevaluation. All biopsies were evaluated for Th1, Th2 and Treg cell counts by means of their transcription factors (T-bet, GATA-3 and FoxP3) using an immunohistochemical analysis method. Additionally, all NLF specimens were evaluated for the functions of these cells, by means of their specific cytokines, using an ELISA method.
RESULTS: When the basal status of those patients with SAR was evaluated based on transcription factors, prior to treatment, Th1 and Treg cells were found to be fewer than in non-allergic controls (p=0.001 for both T-bet and FoxP3). It was demonstrated that numbers of GATA-3-carrying cells, which are a marker for Th2, were not significantly different between the groups (p=0.276), but evaluation of the Th1/Th2 ratio revealed a relative Th2 dominance in patients with SAR prior to treatment. When evaluated on the basis of cytokine levels, it was observed that Th1-originated IFN-γ was lower in patients with SAR compared to the control group, both before and after treatment (p=0.012 for both comparisons), Th2-originated IL-4 levels were not significantly different between the groups either before or after treatment (p=0.649, p=0.855; respectively). Th2- and Treg cell-originated IL-10 levels were higher in patients with SAR before treatment (p=0.033), but this difference was not statistically signifant following treatment compared with controls (p=0.174). Treg cell-originated TGF-β levels were slightly lower in patients with SAR compared to the controls, although the difference was not statistically significant (p=0.178, p=0.296; respectively). None of the above mentioned cytokine levels changed significantly as a result of SIT.
CONCLUSION: The results of our study indicate that although clinical findings improve after one year of SIT, this duration may not be sufficient to detect changes in cytokine patterns and transcription factors. Further studies that evaluate outcome over a longer duration of treatment would provide valuable information.