Serum levels of interleukin 33 and its receptor ST2 in patients treated with subcutaneous allergen immunotherapy in intermittent allergic rhinitis

Introduction
Interleukin 33 (IL-33) is a pleiotropic cytokine involved in pathological processes in seasonal allergic rhinitis. IL-33 binds to ST2 receptor, which is highly expressed on mast cells and selectively on Th2 cells. Information is lacking on the role of IL-33/ST2 axis in allergen subcutaneous immunotherapy.

Aim of the study
To determine if allergen immunotherapy changes the IL-33/ST2l axis in seasonal allergic rhinitis patients.

Material and methods
40 patients with intermittent allergic rhinitis sensitive to grass and/or tree pollen were studied. Among these, 10 patients were longitudinally assessed in the follow-up visit after completing the first course of immunotherapy. Twenty-two healthy subjects were included as controls. Immunotherapy was applied according to a perennial schedule comprising up-building and maintenance phases. Serum levels of ST2/IL-33 R and IL-33 were measured by ELISA (R&D Systems).

Results
Serum levels of IL-33 significantly rose after the first course of immunotherapy and reached the controls levels. Serum levels of ST2 were comparable before the pollen season and after the first course of immunotherapy.

Conclusions
Increase in serum levels of IL-33 after the first course of immunotherapy may suggest it is too short period to prevent the expected raise in serum IL-33 levels in the pollen season, and longer treatment is required to observe significant changes of this cytokine. ST2 serum levels are independent of immunotherapy and pollen season.