, 2001; Garn & Renz, 2007). Suppression

of Th2 and induction of Th1 cytokine production and induction of T-regulatory (Treg) cells could thus be beneficial in treating allergic diseases by antagonizing the Th2 cell development, resulting in suppressed IgE formation (Romagnani, 2004; Fink, 2010). A proposed effect of probiotics is down-regulation of the Th2 cytokine production either by stimulation of Th1 cytokines or by stimulation of the regulatory cytokine click here IL-10, produced by antigen-presenting cells such as monocytes (Pochard et al., 2002; Niers et al., 2005; Ghadimi et al., 2008). Furthermore, the activities of Th1 and Th2 are suppressed via IL-10 and TGF-β production by Treg cells, to help in balancing the intestine (Haller et al., 2000; Pessi et Selleck MK-2206 al., 2000; Rautava et al., 2005; Garn & Renz, 2007). Deficiency in functional Treg cells is currently widely accepted as a possible mechanism underlying the Th2-skewed response in allergy (Larche, 2007; Akdis & Akdis, 2009). Lactobacilli can upregulate the induction of Treg cells, triggering the release of regulatory cytokines and controlling the delicate balance between Th1 and Th2 immunity as well as tolerance (Savilahti et al., 2008; de

Roock et al., 2010; Fink, 2010; Kwon et al., 2010). The differential effects of probiotic strains are frequently investigated in vitro using human peripheral blood mononuclear cell (hPBMC) but generally derived from healthy donors (Miettinen CYTH4 et al., 1996; Chen et al., 1999; Kankaanpaa et al., 2003; Drouault-Holowacz et al., 2006), and only a few studies have investigated the in vitro response of probiotics to hPBMC of allergic patients (Pochard et al., 2002; Flinterman et al., 2007; Rasche et al., 2007; Ghadimi et al., 2008). Healthy subjects, in contrast to allergic individuals, are assumed to regulate the Th1/Th2 balance by inducing sufficient Treg cell activity to maintain or restore immune tolerance

to allergens (Akdis & Akdis, 2009; Fink, 2010). The aim of the present study was to investigate the immunomodulatory capacity of six selected Lactobacillus strains and one mixture of two strains on hPBMC of pollen-allergic patients. Birch- and grass pollen-allergic patients were chosen as these are common seasonal allergies, with a prevalence estimated up to 40% (D’Amato et al., 2007), and a possible benefit of probiotics could thus be of interest for a large part of the population. Human trials on probiotics have shown promising results for prevention of atopic eczema; however, the results on possible benefits for management of inhalant allergies, such as hay fever are not as conclusive (Vliagoftis et al., 2008; Kalliomaki et al., 2010).