Innate and adaptive immune responses to the major Parietaria allergen Par j 1 in healthy subjects.

In this study we wanted to analyse the pattern of the immune response to the Parietaria major allergen Par j 1 in freshly purified peripheral blood mononuclear cell (PBMC) from healthy subjects. We observed that Par j 1 was capable of inducing IFN-γ production by CD3⁻ and CD16⁺/CD56⁺ cells exclusively in healthy individuals. Furthermore, a multiparametric analysis allowed us a better definition of two IFN-γ-Par j 1 specific populations (IFN-γ(dim) and IFN-γ(high)) characterized by the presence of different proportions of NKT and NK cells. We also identified the concomitant presence of a subset of IL-10⁺ NK cells. Moreover, CFSE staining showed that the Par j 1 preferentially induced the proliferation of CD3⁻/CD56⁺/CD335⁺ cells. Finally, a subset of CD4⁺/CD25⁺/FoxP3⁺/IL-10⁻ T cells was identified. The result of this pilot study suggest that during a tolerogenic response, the major allergen of the Parietaria pollen works as an activator of both the innate and the adaptive human immune system.