Gene expression profiling of human donor T cells before allogeneic hematopoietic cell transplantation revealed that expression of selected genes correlated with the occurrence of graft-versus-host disease (GVHD) in recipients. The gene with the best GVHD predictive accuracy was SMAD3, a core component of the transforming growth factor-␤ signaling pathway, whose expression levels vary more than a 6-fold range in humans. The putative role of SMAD3 in the establishment of graft-host tolerance remained elusive. We report that SMAD3-KO mice present ostensibly normal lymphoid and myeloid cell subsets. However, the lack of SMAD3 dramatically increased the frequency and severity of GVHD after allogeneic hematopoietic cell transplantation into major histocompatibility complex-identical recipients. Lethal GVHD induced by SMAD3-KO donors affected mainly the intestine and resulted from massive tissue infiltration by T-bet ؉ CD4 T cells and granulocytes that caused tissue damage by in situ release of Th1 cytokines and oxidative-nitrosative mediators, respectively. Our report reveals the nonredundant roles of SMAD3 in the development of tolerance to the host. Furthermore, our data support the concept that SMAD3 levels in donor cells dictate the risk of GVHD and that SMAD3 agonists would be attractive for prevention of GVHD. (Blood. 2011;117(5):1734-1744) IntroductionAfter decades of intensive research, graft-versus-host disease (GVHD) remains the unrelenting nemesis of patients and physicians involved in allogeneic hematopoietic cell transplantation (AHCT). 1-3 A better understanding of GVHD pathophysiology could lead to a more widespread use of AHCT, an otherwise potent treatment for hematologic malignancies and other less common diseases. GVHD is a complex immunopathology that hinges on recognition of host alloantigens by donor T cells. [4][5][6] Importantly, although histoincompatibility between donor and recipient is necessary, it is not sufficient to elicit GVHD. Of particular relevance, some donors are more dangerous than others. Indeed, a comprehensive study of CD4 and CD8 T cells from 50 human donor-recipient pairs revealed that pre-AHCT gene expression profiling segregates donors whose recipient did or did not have GVHD. 7 The gene with the best GVHD predictive accuracy was SMAD3. No AHCT recipients had GVHD when their donor cells expressed high levels of SMAD3 transcripts. 7 SMAD3 mRNA levels are stable over time in a given person but present substantial interindividual differences as they were found to vary more than a 6-fold range in a cohort of 397 subjects. 8 At least in transfected cells, SMAD3 protein levels correlate with expression of SMAD3 transcripts and with the strength of SMAD3 signaling. 9-11 Moreover, TCR signaling leads to commensurate decreases in expression of SMAD3 transcripts and phosphorylated SMAD3 protein. 12 Proteins of the SMAD family are homologous to proteins encoded by the Caenorhabditis elegans gene Sma and the Drosophila gene Mad. SMAD3 is one of the 2 "receptor-SMADs" that transduce tr...

Graft-versus-host disease (GVHD) impairs immune reconstitution after allogeneic stem cell transplantation (allo-SCT) and effective therapies aimed at restoring T cell counts in GVHD patients have yet to be developed. During GVHD, CD4(+) T cell reconstitution is particularly affected and current models hold that GVHD insult to the peripheral lymphoid niche is responsible for this effect. Here, we show that naïve CD4(+) T cell homeostatic proliferation (HP) is lost during GVHD because of low systemic IL-7 and impaired dendritic cell (DC) regeneration. We assessed factors involved in DC differentiation and found that although fms-like tyrosine kinase 3 ligand (Flt3-L) levels were normal, stromal-derived factor-1α (SDF-1α) was diminished in the blood of GVHD mice. Unlike Flt3-L treatment, the administration of SDF-1α specifically increased CD8α(+) DC numbers and did not worsen GVHD. Importantly, CD4(+) T cell HP was enhanced only when IL-7 and SDF-1α or Flt3L were coadministered, confirming the crucial role of DCs and IL-7 in restoring CD4(+) T cell regeneration during GVHD. Altogether, our results indicate that CD8α(+) DCs are part of the peripheral niche that controls CD4(+) T cell HP and that their depletion, combined with low systemic IL-7, explains how GVHD constrains naïve CD4(+) T cell reconstitution after allo-SCT.

Key Points• TCR stimulation increases IL-7 responsiveness.• CD4 1 SPT proliferate more 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 1 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 1 CD8 2 thymocytes compared with peripheral CD4 1 T cells. These cells express miR181a at higher levels and respond to lower concentrations of IL-7. As singlepositive CD4 1 thymocytes (CD4 1 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 1 T cells, whereas failure to stimulate TCR abrogates proliferation induced by IL-7. Finally, we demonstrated that IL-7 enhances the proliferation of CD4 1 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. (Blood. 2013;121(23):4684-4693)

Five enzymes involved in glutamic acid, GABA, and catecholamine metabolism were measured in epileptic human brain. Electrocorticographically defined areas of focal spiking were compared with samples from surrounding nonspiking cortex. Comparative enzyme activities were as follows (mumol/h/g wet wt): glutamic acid dehydrogenase (GDH)--spiking 135.77 +/- 10.22 (mean +/- SEM), nonspiking 118.58 +/- 9.42 (p less than 0.001, N = 17); glutamic acid decarboxylase--spiking 10.63 +/- 0.95, nonspiking 9.96 +/- 1.10 (NS, N = 13); GABA-aminotransferase--spiking 36.49 +/- 1.05, nonspiking 36.46 +/- 1.48 (NS, N = 12); glutamine synthetase--spiking 96.94 +/- 3.81, nonspiking 96.52 +/- 4.10 (NS, N = 20); and tyrosine hydroxylase (TH; nmol/h/g)--spiking 16.23 +/- 2.39, nonspiking 10.67 +/- 1.95 (p less than 0.001, N = 14). Increased activity of GDH and TH may prove useful to characterize further areas of active spiking in human focal epilepsy.