Acute graft-versus-host disease (GVHD) is a major complication of allogeneic stem cell transplantation (SCT) and can be readily controlled by systemic high-dose steroids in many patients. However, patients whose GVHD is refractory to this therapy have a poor prognosis. Refractory patients have ongoing end-organ damage despite effective immunosuppression with second-line regimens, suggesting pathomechanisms independent from the initiating T-cell attack. To explore whether endothelial damage might contribute to GVHD refractoriness and to study the role of angiopoietin-2 (ANG2) in this process, we have compared kinetics of T-cell activation markers and markers of endothelial dysfunction in the serum of patients with sensitive (n ‫؍‬ 23) and refractory GVHD (n ‫؍‬ 25). Longitudinal measurements of soluble FAS ligand along with other immune markers demonstrate that refractory patients are not exposed to an overwhelming or unresponsive Tcell attack. However, in contrast to sensitive GVHD, refractory GVHD was associated with rising thrombomodulin levels and high ANG2/ vascular endothelialderived growth factor ratios. Patients with refractory GVHD showed significantly increased ANG2 levels already before SCT. These results suggest that endothelial cell vulnerability and dysfunction, rather than refractory T-cell activity, drives treatment refractoriness of GVHD and opens new avenues for prediction and control of this devastating condition. (Blood. 2011; 118(6):1685-1692)

The key components of the intracellular molecular network required for the expression of a specific function of dendritic cells (DCs) are as yet undefined. Using an in vitro model of human monocyte-derived DC differentiation, this study investigates the role of glycogen synthase kinase 3 (GSK-3), a multifunctional enzyme critical for cellular differentiation, apoptosis, self-renewal, and motility, in this context. We demonstrate that GSK-3(1) inhibits macrophage development during differentiation of DCs, (2)

Graft-versus-host disease (GVHD) is the main complication of allogeneic stem cell transplantation. However, diagnosis of GVHD and evaluation of response to immunosuppressive treatment is sometimes difficult. Since apoptosis is the histopathologic hallmark in GVHD, we investigated whether active GVHD-induced target organ destruction is mirrored by serum levels of the caspasecleaved neo-epitope of cytokeratin-18 fragments (CK18Fs). Serum CK18F kinetics was monitored by M30 antibodybased enzyme-linked immunosorbent assay (ELISA) in 50 patients who fulfilled histopathologic and/or clinical criteria diagnostic for GVHD. Both intestinal and hepatic GVHD were consistently associated with significant elevations of CK18F levels over baseline. Responses of GVHD to immunosuppressive therapy were paralleled by CK18F decreases, whereas resistant GVHD was characterized by persistent CK18F rises. Clinical conditions that might represent relevant differential diagnoses, such as toxic mucositis, noncomplicated, infection-related diarrhea, and veno-occlusive disease were not associated with CK18F elevations. In conclusion, CK18F monitoring provides a serum marker for quantitative assessment of GVHD-associated apoptotic activity in intestinal and hepatic GVHD. Although apoptosis is not GVHD-specific, CK18Fs may help to distinguish active GVHD from GVHD-unrelated conditions with similar symptoms, and to monitor response to immunosuppressive treatment. Prospective studies are warranted to evaluate how CK18Fs may assist in the diagnosis, grading, and treatment guidance of GVHD.