We thank Dr Tânia C. Felizardo

for the donation of anti-mouse IFN-γ mAb (hybridoma XMG 1.2). The authors gratefully acknowledge Dr. Telma M.T. Zorn and Dr. Sebastian A. San-Martin check details (Department of Cell and Developmental Biology, Institute of Biomedical Sciences – University of São Paulo, Brazil) for helping with the immunohistochemical reactions. “
“γ-chain (γc) cytokine receptor signaling is required for the development of all lymphocytes. Why γc signaling plays such an essential role is not fully understood, but induction of the serine/threonine kinase Pim1 is considered a major downstream event of γc as Pim1 prevents apoptosis and increases metabolic activity. Consequently, we asked whether Pim1 overexpression would suffice to restore lymphocyte development in γc-deficient mice. By analyzing Pim1-transgenic γc-deficient mice (Pim1TgγcKO), we show that Pim1 promoted T-cell development and survival in the absence of γc. Interestingly, such effects were largely limited to CD4+ lineage αβ T cells as CD4+ T-cell numbers

improved to near normal levels but CD8+ T cells remained severely lymphopenic. Notably, Pim1 over-expression failed to promote development and survival of any T-lineage cells other than αβ T cells, as we observed complete lack of γδ, NKT, FoxP3+ T regulatory cells and TCR-β+ CD8αα IELs in Pim1TgγcKO selleck inhibitor mice. Collectively, these results uncover distinct requirements for γc signaling between CD4+ αβ T cells and all other T-lineage cells, and they

identify Pim1 as a novel effector molecule very sufficient to drive CD4+ αβ T-cell development and survival in the absence of γc cytokine receptor signaling. All T-lineage lymphocytes depend on two nonredundant signals for their development and differentiation in the thymus. One signal is mediated by the T-cell antigen receptor (TCR) that induces thymocyte differentiation [1, 2], the other signal is mediated by cytokines of the common γ-chain (γc) cytokine family that is proposed to be essential for cell survival [3]. In the absence of either one of these signals, T-cell development in the thymus is critically impaired [4-7]. The developmental requirements for TCR signals are rather well defined. TCR signals terminate expression of recombination activating genes (RAG) and fix the specificity of the TCR [8]. TCR signals also upregulate expression of the TCR itself and induce expression of antiapoptotic molecules and cytokine receptors [8, 9]. In contrast, the role of γc signaling remains less understood. γc signals are primarily considered as survival factors, but recent data also suggested new roles for γc beyond its prosurvival function.