TCR triggering modulates the responsiveness and homeostatic proliferation of CD4+ thymic emigrants to IL-7 therapy.

Interleukin-7 (IL-7) is currently used in clinical trials to augment T-cell counts. Paradoxically, elevated systemic IL-7 found in lymphopenic humans is typically insufficient for CD4(+) T-cell regeneration, and thymopoiesis becomes critical in this process. Here we show that the proliferative effect of IL-7 is more pronounced on CD4(+)CD8(-) thymocytes compared with peripheral CD4(+) T cells. These cells express miR181a at higher levels and respond to lower concentrations of IL-7. As single-positive CD4(+) thymocytes (CD4(+)(SPT)) exit the thymus, they rapidly diminish their proliferation to IL-7 therapy, and this is mediated, at least in part, by major histocompatibility complex class II distribution outside the thymus. Interestingly, increasing T-cell receptor (TCR) stimulation augments IL-7 responsiveness and proliferation of peripheral CD4(+) T cells, whereas failure to stimulate TCR abrogates proliferation induced by IL-7. Finally, we demonstrated that IL-7 enhances the proliferation of CD4(+) T cells that undergo "slow proliferation" in lymphopenic hosts. To date, our results indicate that TCR signaling is a major controlling factor for CD4 responsiveness and proliferation to IL-7 therapy.

Redefining interferon-producing killer dendritic cells as a novel intermediate in NK-cell differentiation.

The cell lineage origin of IFN-producing killer dendritic cells (IKDCs), which exhibit prominent antitumoral activity, has been subject to debate. Although IKDCs were first described as a cell type exhibiting both plasmacytoid DC and natural killer (NK) cell properties, the current view reflects that IKDCs merely represent activated NK cells expressing B220, which were thus renamed B220+ NK cells. Herein, we further investigate the lineage relation of B220+ NK cells with regard to other NK-cell subsets. We surprisingly find that, after adoptive transfer, B220- NK cells did not acquire B220 expression, even in the presence of potent activating stimuli. These findings strongly argue against the concept that B220+ NK cells are activated NK cells. Moreover, we unequivocally show that B220+ NK cells are highly proliferative and differentiate into mature NK cells after in vivo adoptive transfer. Additional phenotypic, functional, and transcriptional characterizations further define B220+ NK cells as immediate precursors to mature NK cells. The characterization of these novel attributes to B220+ NK cells will guide the identification of their ortholog in humans, contributing to the design of potent cancer immunotherapies.

Adoptive transfer of CD4+CD25+ regulatory cells combined with low-dose sirolimus and anti-thymocyte globulin delays acute rejection of renal allografts in Cynomolgus monkeys.

Although donor alloantigen specific Treg cells play an important role in transplant tolerance, therapeutic applications are limited by their low frequency. In this study, isolated Tregs from Cynomolgus monkeys were efficiently expanded by a co-culture system, and maintained suppressive function on the proliferation of CD4(+) effector cells in vitro. Adoptive transfer of expanded donor alloantigen specific Tregs without any immunosuppressants could prolong survival of MHC-mismatched allografts in Cynomolgus monkeys. To reach the feasibility of clinical transplantation, our objectives focused on whether exposure of monkey Tregs to immunosuppressants could preserve suppressive function in vitro and in vivo. The results showed that low-dose sirolimus selectively expanded Tregs, increased the expression of CD25(bright) and Foxp3 markers, and suppressed TCR- or allo-antigens induced CD4(+) T cell proliferation in vitro. In vivo, after pre-treated with anti-thymocyte globulin (ATG) for consecutive 3days, a 14-day therapy of adoptive infusion of donor alloantigen-specific Tregs combined with low-dose sirolimus delayed acute rejection of renal allografts in Cynomolgus monkeys, showing an MST of 48.5days as compared with those of untreated and sirolimus-treated monkeys (7days and 22days). The frequencies of CD4(+)CD25(bright) T cells were significantly elevated in mesenteric lymph nodes vs. those in inguino lymph nodes and peripheral blood. In summary, expanded donor alloantigen specific Tregs exposed to sirolimus can preserve inhibition in vitro and in vivo. Tregs are more resistant to sirolimus than other T cells. Expanded donor alloantigen specific Tregs combined with sirolimus and ATG prolongs renal allograft survival in monkeys, suggesting that sirolimus might be one of the best synergists for Tregs therapy.

Combined therapy of CD4(+)CD25(+) regulatory T cells with low-dose sirolimus, but not calcineurin inhibitors, preserves suppressive function of regulatory T cells and prolongs allograft survival in mice.

Our previous study proved that sirolimus is a potent immunosuppressant which induces long-term allograft survival depends on persistence of alloantigens. CD4(+)CD25(+) regulatory T (Treg) cells are potent suppressors in transplantation. Our objectives focus on whether combined-therapy of Tregs with immunosuppressants could prolong allograft survival in mice. The study showed that inhibition of Tregs was maintained by co-cultured with sirolimus (1 nM) in vitro, but not tacrolimus (1 nM) or CsA (1 nM). When the concentration was increased >100 nM, suppression was fallen. Based on the ability of sirolimus to target effector T cells, but retaining the inhibition of Tregs, an adoptive infusion of donor alloantigen specific Tregs combined with 30-day sirolimus (1 mg/kg) and 3-day ATG (20 mg/kg) was found to prolong heart allograft survival in mice. Even though the cell numbers of CD4(+) T cells were found to decrease in sirolimus-treated mice, sirolimus selectively enhanced the numbers of CD4(+)CD25(+) cells and increased the expression of Foxp3 in spleens and lymph nodes, respectively, in recipients. However, combined therapy with low-dose CsA (5 mg/kg) or tacrolimus (1 mg/kg) reduced significantly the expression of Foxp3 and failed to prolong the allograft survival. In summary, expanded Tregs exposed to sirolimus can survive, proliferate, and preserve inhibition in vitro. Tregs are more resistant to sirolimus than other T cells. Combined with Tregs, sirolimus rather than calcineurin inhibitors, prolongs the allograft survival. Sirolimus may be the best copartner for Tregs therapy. It also suggests calcineurin-dependent signals may be required in the development of Tregs.

A novel negative regulatory element in the human collagenase-3 proximal promoter region.

We have identified in the human collagenase-3 promoter a novel negative regulatory element, GAAAAGAAAAAG, designated AGRE (AG-Rich Element). The AGRE site functionality was characterized in human osteoarthritic (OA) chondrocytes as well as four cell lines. The cells were transfected with a plasmid consisting of the first 133 bp of the collagenase-3 promoter and its AGRE mutated or deleted derivatives. The absence of a functional AGRE site resulted in a statistically significant increase of the collagenase-3 basal transcription that was not affected by the collagenase-3 inducers IL-1beta and TGF-beta1. Two specific protein-AGRE binding complexes were detected by EMSA, and their presence depended on the physiological state of the cell. Indeed, normal chondrocytes and synovial fibroblasts and the four cell lines showed only a slower-migrating complex (complex 1). In OA chondrocytes, the type of complex discriminated two groups--the low-OA chondrocytes, showing low collagenase-3 basal levels and high inducibility of IL-1beta stimulation (complex 1), and the high-OA chondrocytes with high collagenase-3 basal levels and low IL-1beta inducibility (a faster-migrating complex, designated complex 2). UV cross-linking revealed the presence of 48 and 97 kDa proteins in complex 1 and 27, 35, and 73 kDa proteins in complex 2. These findings suggest that the AGRE site plays a rate-limiting role in human collagenase-3 production.