All the other data were compared using the Mann–Whitney U-test corrected for multiple comparisons. A P-value of less than 0·05 was considered significant. CTLA-4–Ig was combined with SIT

to examine whether it augments the suppressive effects of SIT in a mouse model of allergic asthma (Fig. 1). OVA-sensitized placebo-treated mice exhibit a strong OVA-specific IgE response, airway eosinophilia and AHR upon OVA inhalation challenges (Fig. 2a–c). OVA-SIT treatment reduced the level of these three basic manifestations of allergic asthma significantly (P < 0·05, Fig. 2a–c), but did not affect significantly the levels of IL-4 and IL-5 in lung tissue (Fig. 2d,e). Co-administration of CTLA-4–Ig with SIT highly augmented the SIT-induced suppression selleckchem of AHR (P < 0·05), OVA-specific IgE (P < 0·005) and airway eosinophilia (P < 0·005) compared to SIT alone. Combination of CTLA-4–Ig with SIT also induced a reduction in the levels of IL-4 (P < 0·05) and IL-5 (P < 0·05) in lung tissue, which was not observed with SIT treatment alone (Fig. 2d,e). Because CTLA-4–Ig has been shown to increase the expression of IDO and thereby induce tolerogenic

effects [31], we tested whether the augmenting effect of CTLA-4–Ig AZD8055 chemical structure on SIT in our model is dependent upon IDO activity. To this aim we compared the effects of co-administration of CTLA-4–Ig with SIT between IDO-KO and wild-type BALB/c mice. OVA-SIT alone suppressed AHR (P < 0·05), specific IgE in serum (P < 0·05) and airway eosinophilia (P < 0·05) in wild-type mice significantly (Fig. 3a,c,d). Co-administration of CTLA-4–Ig with OVA-SIT increased the suppression levels of AHR (P < 0·05),

OVA-specific IgE in serum (P < 0·05) and airway eosinophilia (P < 0·05) significantly, compared to OVA-SIT alone in wild-type mice (Fig. 3a,c,d). In IDO-KO mice, OVA-SIT suppressed airway eosinophilia significantly (P < 0·05), but neither AHR nor specific OVA-specific IgE levels were suppressed (Fig. 3b–d). Surprisingly, co-administration of CTLA-4–Ig with OVA-SIT in IDO-KO mice also strongly enhanced SIT-induced suppression of the manifestation Tideglusib of experimental allergic asthma, resulting in significant suppression of OVA-specific IgE and AHR, which was not achieved by the OVA-SIT alone, and significantly augmented suppression of eosinophils (Fig. 3b–d). These data indicate that although SIT treatment is less efficient in IDO-KO mice, CTLA-4–Ig co-administration remains effective in enhancing the suppressive effects of the OVA-SIT. To evaluate whether administration of CTLA-4–Ig results in the induction of Treg cells, which might suppress reactivation of Th2 cells upon allergen inhalation challenge, we analysed the frequency of CD4+CD25+FoxP3+ Treg cells and CD4+T1ST2+ Th2 cells in peripheral blood 24 h after OVA-SIT. Solo treatment of OVA-SIT alters neither the frequency of CD4+CD25+FoxP3+ Treg cells nor the frequency of CD4+T1ST2+ Th2 cells (Fig. 4a,b).