33 Interestingly, in patients with asthma, it has been shown that airway-infiltrating CD8+ T cells have the ability to produce Th2 cytokines.34–36 Moreover, using the model of OVA-induced allergic airway inflammation, it was shown that CD8+ T cell-depleted mice did not develop AHR, and that this failure was associated with the inability to recruit eosinophils into the lung as a result of diminished 3-Methyladenine datasheet production of IL-5.37,38 In the present study, we found that adoptive transfer of OVA-pulsed DCs previously

treated with histamine to allergic mice resulted in the selective stimulation of lung infiltration by CD8+ T cells but not by CD4+ T cells. These cells did not produce IFN-γ but a subpopulation of them produced IL-5, suggesting that they had differentiated into cells with a CD8+ T-cell type 2 profile. Interestingly, these changes were associated with a significant increase in the serum levels of specific IgE antibodies directed to OVA and more persistent lung infiltration by eosinophils. This last effect could be attributable to the higher levels of IL-5 in the lungs

of mice treated with DCHISs. Histamine plays a critical role in immediate-type allergic reactions, and also modulates the function of DCs.31,39,40 Histamine inhibits IL-12 and increases IL-10 production by activated DCs, promoting the differentiation of CD4+ T cells into cells with a Th2 profile,5,8 and thus increasing the severity of atopic diseases. Histamine also Talazoparib order induces the chemotaxis of immature DCs.7 Moreover, it has been shown that histamine is produced during the differentiation of DCs and that inhibition of histamine biosynthesis results in the impairment of DC development.41 We previously reported a new mechanism through which histamine might modulate the function of DCs.10 We found that histamine stimulates cross-presentation of soluble antigens by DCs. Thus, histamine may enhance the ability of DCs to activate CD8+ T cells. This mechanism, however, does not explain the greater ability

of DCHISs to induce the recruitment of CD8+ T cells in the lung. This response could be related to the higher production of LTB4, a master chemotactic stimulus for CD8+ T cells,24,42 by DCs isolated from the lungs of allergic mice treated with DCHISs. Our results reveal a new pathway through which histamine, via its Phosphoprotein phosphatase effects on DCs, may increase the severity of allergic airway inflammation. Further experiments are required to elucidate the underlying mechanisms by which DCHISs stimulate lung infiltration by CD8+ T cells and their differentiation into cells with a type 2 profile. We thank Beatriz Loria and Edith Mabel Horvat for their technical assistance. This work was supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), School of Medicine, Buenos Aires University, and Agencia Nacional de Promoción Científica y Tecnológica, Argentina. The authors have no conflicts of interest to disclose.