Regulatory Lymphocytes (Treg) in the Modulation of Allergic Inflammation in Patients Treated With Specific Immunotherapy.

Allergy constitutes an important problem worldwide thus effective treatment is crucial for the reduction of symptoms severity, patients' activity and quality of life as well as for the reduction of direct and indirect costs of the disease. Specific allergen immunotherapy (SIT) is a potentially curative and specific method of treatment for allergic diseases, particularly for intermittent allergic rhinitis. Specific subcutaneous immunotherapy induce peripheral tolerance and suppress inflammation in tissue. In periphery, effector T cells unresponsiveness to antigens is mediated mainly by allergen specific regulatory T cells. Regulatory T cells induced peripherally comprise IL-10 producing type 1 regulatory T cells (Tr1) and regulatory T cells subset arising in vitro from CD4+CD25- and in vivo from peripheral memory T cells whereas naturally occurring Tregs (nTregs)originate in thymus and represent about 5% of the peripheral CD4 T cells and constitutively express high levels of the high-affinity IL-2 receptor (CD25hi). They coexpress Forkhead Box Protein P3 (Foxp3), glucocorticoid induced tumor necrosis factor receptor (GITR), cytotoxic T lymphocyte associated antigen (CTLA-4), and display low expression of alpha chain of the IL-7 receptor. Although clinical and immunological outcomes of SIT, that are associated with regulatory T cells functions were profoundly studied, little is known about the molecular mechanisms that are crucial for nTregs activation and function in the course of SIT. Since histamine is a key mediator in allergy that exerts its effect through 4 types of histamine receptors we decided to investigate the expression of histamine 2 receptor, that has potent immunomodulatory properties, in regulatory lymphocytes in patients treated with SIT. Furthermore, since T cell receptor activation is essential for T effector lymphocytes activation we wanted to check the expression of zeta chain associated protein (ZAP70), that constitutes a linker between TCR and lower levels of intracellular downstream signal transduction, in regulatory T cells in the course of SIT.

This is a 3-year prospective, placebo controlled, double blind trial of grass SIT. 41 patients with seasonal allergic rhinitis were randomized to receive SIT (n = 21) or placebo (n = 20) and 15 healthy were included as a control. The primary and secondary outcomes were assessed at baseline and during the treatment period - before the start of the pollen season, at the height of the pollen season and after the end of the pollen season.Results were compared between the treatment year and baseline and between the groups treated with SIT, placebo and healthy control.