Biology of chronic graft-versus-host disease: implications for a future therapeutic approach.

Hematopoietic cell transplantation (HCT) is frequently complicated by graft-versus-host disease (GVHD). During the past three decades, experimental studies and clinical observations have elucidated the pathophysiology of acute GVHD, but the biology of chronic GVHD is much less well understood. Recommendations of the NIH Consensus Development Project on Criteria for Clinical Trials in Chronic GVHD have begun to standardize the diagnosis and clinical assessment of the disease. These criteria have emphasized the importance of qualitative differences, as opposed to time of onset after HCT, in making the distinction between acute and chronic GVHD. Experimental studies have generated at least four theories to explain the pathophysiology of chronic GVHD. These theories include 1) thymic damage and defective negative selection of T cells generated from marrow progenitors after HCT, 2) aberrant production of transforming growth factor-beta, 3) auto-antibody production, and 4) deficiency of T-regulatory cells. Recent studies in humans have corroborated a possible role for each of these mechanisms in humans. No animal model fully replicates all of the features of chronic GVHD in humans, and it appears likely that multiple biological mechanisms account for the diverse features the disease. Chronic GVHD may represent a "syndrome" with diverse causes among individual patients. In the future, it might become possible to tailor specific therapeutic interventions for patients as individually needed for each distinct pathophysiologic mechanism involved in development of the disease

Early Alteration of Nucleocytoplasmic Traffic Induced by Some RNA Viruses

AbstractA HeLa cell line expressing the green fluorescent protein fused to the SV40 T-antigen nuclear localization signal (EGFP-NLS) was established. Fluorescence in these cells was confined to the nuclei. After poliovirus infection, cytoplasmic fluorescence in a proportion of cells could be detected by 1 h postinfection (p.i.) and in virtually all of the fluorescent cells by 2 h p.i. The relocation could be prevented by cycloheximide but not by inhibition of poliovirus replication by guanidine · HCl. Nuclear exit of a protein composed of three copies of GFP fused to the NLS also occurred upon poliovirus infection. A similar redistribution of EGFP-NLS took place upon infection with coxsakievirus B3 and, to a lesser extent, with vesicular stomatitis virus. The EGFP-NLS efflux was not due to the loss of NLS. Thus, some positive-strand and negative-strand RNA viruses trigger a rapid nonspecific relocation of nuclear proteins

Regulatory T Cell-Derived Interleukin-10 Limits Inflammation at Environmental Interfaces

SummaryThe regulatory T (Treg) cells restrain immune responses through suppressor-function elaboration that is dependent upon expression of the transcription factor Foxp3. Despite a critical role for Treg cells in maintaining lympho-myeloid homeostasis, it remains unclear whether a single mechanism or multiple mechanisms of Treg cell-mediated suppression are operating in vivo and how redundant such mechanisms might be. Here we addressed these questions by examining the role of the immunomodulatory cytokine IL-10 in Treg cell-mediated suppression. Analyses of mice in which the Treg cell-specific ablation of a conditional IL-10 allele was induced by Cre recombinase knocked into the Foxp3 gene locus showed that although IL-10 production by Treg cells was not required for the control of systemic autoimmunity, it was essential for keeping immune responses in check at environmental interfaces such as the colon and lungs. Our study suggests that Treg cells utilize multiple means to limit immune responses. Furthermore, these mechanisms are likely to be nonredundant, in that a distinct suppressor mechanism most likely plays a prominent and identifiable role at a particular tissue and inflammatory setting

Nuclear Oncoprotein Prothymosin α Is a Partner of Keap1: Implications for Expression of Oxidative Stress-Protecting Genes

Animal cells counteract oxidative stress and electrophilic attack through coordinated expression of a set of detoxifying and antioxidant enzyme genes mediated by transcription factor Nrf2. In unstressed cells, Nrf2 appears to be sequestered in the cytoplasm via association with an inhibitor protein, Keap1. Here, by using the yeast two-hybrid screen, human Keap1 has been identified as a partner of the nuclear protein prothymosin α. The in vivo and in vitro data indicated that the prothymosin α-Keap1 interaction is direct, highly specific, and functionally relevant. Furthermore, we showed that Keap1 is a nuclear-cytoplasmic shuttling protein equipped with a nuclear export signal that is important for its inhibitory action. Prothymosin α was able to liberate Nrf2 from the Nrf2-Keap1 inhibitory complex in vitro through competition with Nrf2 for binding to the same domain of Keap1. In vivo, the level of Nrf2-dependent transcription was correlated with the intracellular level of prothymosin α by using prothymosin α overproduction and mRNA interference approaches. Our data attribute to prothymosin α the role of intranuclear dissociator of the Nrf2-Keap1 complex, thus revealing a novel function for prothymosin α and adding a new dimension to the molecular mechanisms underlying expression of oxidative stress-protecting genes