ELISPOT and ELISA assessment of interferon-gamma after sublingual immunotherapy

Allergic rhinitis (AR) is characterized by a Th2 polarized immune response, and specific immunotherapy modifies this arrangement, restoring a physiologic Th1 profile. Sublingual immunotherapy (SLIT) is widely prescribed. The aim of the study is to evaluate two different methods for assessing IFN-γ, namely ELISPOT and ELISA, before and after a pre-seasonal SLIT course as marker for Th1 response. Thirty-eight AR patients with pollen allergy assumed pre-seasonal SLIT for 3 months. Patients' blood samples for assessing IFN-γ serum levels were collected before initiating SLIT (baseline - T0), after 3 months pre-seasonal SLIT course (T1), and three months after completion of SLIT (T2). IFN-γ-specific producing cells, after allergen stimulation, were assessed by cytokine ELISPOT at the same time points. IFN-γ-specific producing cells significantly increased after SLIT both at T1 and T2 (p=0.0002). On the contrary, ELISA assessment did not reveal an increase in IFN-γ serum levels at any time point. In conclusion, these results demonstrate that ELISA assessment of serum IFN-γ is not suitable for identifying an early response.