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Clinical & Experimental Allergy

Decrease of allergen-specific T-cell response induced by local nasal immunotherapy

Authors


Dr Maggi Clinical Immunology Department, Istituto di Medicina Interna e Immunoallergologia, Università di Firenze, Policlinico di Careggi, Viale Morgagni, 85, 50134, Firenze, Italy.

Abstract

Background

The clinical efficacy and safety of local nasal immunotherapy (LNIT) with lyophilized ‘macronized’ powder has been demonstrated. However, the immunological changes possibly induced by LNIT which may account for the clinical improvement are still unclear.

Objective

To investigate the effects of a successful LNIT-treatment on the allergen-driven T cell response, cytokine secretion and IgE and IgG antibody production.

Methods

Three groups (untreated, subcutaneous immunotherapy- SIT- and LNIT-treated) of grass-sensitive patients suffering from seasonal rhinitic symptoms were ramdomized for the 2-year study. The proliferative response of PBMC to purified Rye-1 allergen and serum levels of grass-specific IgE and IgG were evaluated before treatment and during the 2-year subsequent pollination periods. The proliferative response of allergen-specific short-term T-cell lines, as well as production of allergen-driven cytokine by PBMC, were also assessed.

Results

Both SIT and LNIT induced a significant reduction of symptom scores during the pollination season. SIT, but not LNIT, induced a significant change in serum levels of allergen-specific IgE and IgG antibody. By contrast, both SIT and LNIT reduced the increase of the proliferative response of allergen-specific T cells driven by natural allergen exposure and significantly decreased T cell proliferation to low doses of allergen, as shown also by the mitogenic index of allergen-specific T-cell lines. A reduced IL-4 and IFNγ production by PBMC of LNIT- and SIT-treated patients was also observed in the absence of a clearcut TH2-TH1 switch.

Conclusions

These data suggest that a common mechanism of both LNIT and SIT is the induction of T-cell tolerance, thus providing a rational basis to explain why LNIT may be clinically successful in allergic patients with rhinits.

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