Background: A hot new topic in medical treatment is the use of mesenchymal stem cells (MSC) in therapy. The low frequency of this subpopulation of stem cells in bone marrow (BM) necessitates their in vitro expansion prior to clinical use. We evaluated the effect of long term culture on the senescence of these cells.

IL-27 is a member of the IL-12 family of cytokines that is comprised of an IL-12 p40-related protein subunit, EBV-induced gene 3 (EBI3), and a p35-related subunit, p28. IL-27 functions through IL-27R and has been shown to have potent anti-tumor activity via activation of a variety of cellular components, including anti-tumor CD8+ T-cell responses. However, the exact mechanisms of how IL-27 enhances anti-tumor CD8+ T-cell responses remain unclear. Here we show that IL-27 significantly enhances the survival of activated tumor antigen specific CD8+ T cells in vitro and in vivo, and programs tumor antigen-specific CD8+ T cells into memory precursor (MPC)-like effector cells, characterized by upregulation of Bcl-6, SOCS3, Sca-1, and IL-10. While STAT3 activation and the CTL survival-enhancing effects can be independent of CTL IL-10 production, we show here that IL-27-induced CTL IL-10 production contributes to MPC phenotype induction, CTL memory, and tumor rejection. Thus, IL-27 enhances anti-tumor CTL responses via programming tumor antigen-specific CD8+ T cells into a unique memory precursor-type of effector cells characterized by a greater survival advantage. Our results have important implications for designing immunotherapy against human cancer.

Epstein-Barr virus-induced gene 3 (EBI3) encoded protein can form heterodimers with IL-27P28 and IL-12P35 to form IL-27 and IL-35. IL-27 and IL-35 may influence autoimmunity through inhibiting Th17 differentiation, and facilitating the inhibitory roles of Foxp3+ Treg cells, respectively. In this study we have evaluated the development of experimental autoimmune encephalomyelitis (EAE) in EBI3-deficient mice that lack both IL-27 and IL-35. We found that MOG peptide immunization resulted in marginally enhanced EAE development in EBI3-deficient C57BL6 and 2D2 TCR transgenic mice. EBI3-deficiency resulted in significantly increased Th17 and Th1 responses in the central nervous system (CNS) and increased T cell production of IL-2 and IL-17 in the peripheral lymphoid organs. EBI3-deficient and -sufficient 2D2 T cells had equal ability in inducing EAE in Rag1−/− mice, however more severe disease was induced in EBI3−/−Rag1−/− mice than in Rag1−/− mice by 2D2 T cells. EBI3-deficient mice had increased numbers of CD4+FoxP3+ Treg cells in peripheral lymphoid organs. More strikingly, EBI3-deficient Treg cells had more potent suppressive functions in vitro and in vivo. Thus, our data support an inhibitory role for EBI3 in Th17, Th1, IL-2 and Treg responses. While these observations are consistent with the known functions of IL-27, the IL-35 contribution to the suppressive functions of Treg cells is not evident in this model. Enhanced Treg responses in EBI3−/− mice may explain why the EAE development is only modestly enhanced compared to WT mice.

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