Dendritic cells (DCs), as an important part of antigen-presenting cells, can efficiently prime naïve T cell to induce or regulate immune responses. GM-CSF, combined with other growth factors, was used to induce the differentiation of immature or mature DCs from progenitors. Here, we investigated the effect of IL-5, a Th2 cytokine, on the differentiation and function of mouse DCs induced by GM-CSF in vitro. IL-5 significantly inhibited the differentiation of DCs induced by GM-CSF, but no effects on GM-CSF/IL-4 (GM/4) induced DCs. Compared with the conventional mouse DCs developed in the presence of GM-CSF and IL-4, mouse DCs induced by GM-CSF and IL-5 (refereed as to GM/5 DCs) possessed similar cellular morphology, but they expressed high level of CD11c, but low level of MHC II molecules, CD40 and CD86, which is consistent with the immature DC phenotype. In addition, GM/5 DCs showed significantly lower immunogenicity as indicated by their poor stimulating ability to allogeneic T cells in vitro, decreased expression of pro-inflammatory IL-6 and TNF-alpha, as well as increased expression of TGF-beta, compared with GM/4 DCs. Together, these data suggest that IL-5 could partially inhibit GM-CSF-induced DC differentiation which could be reversed by IL-4 in vitro.