IFN-γ has long been recognized as a signature proinflammatory cytokine that plays a central role in inflammation and autoimmune disease. There is now emerging evidence indicating that IFN-γ possesses unexpected properties as a master regulator of immune responses and inflammation. In this issue of the JCI, Guillonneau et al. show that indefinite allograft survival induced by CD40Ig treatment is mediated by CD8+CD45RClow T cells through the production of IFN-γ (see the related article beginning on page 1096), supporting the emerging view that IFN-γ is critical in the self-regulation of inflammation. These contradictory roles of IFN-γ, perhaps best understood by the principle of yin and yang, represent one of nature’s paradoxes, whereby the same cytokine functions as an inducer as well as a regulator for inflammation. Understanding this complex process of IFN-γ signaling is essential, as it has therapeutic implications.
The deregulation of homeobox (HOX) genes in acute myeloid leukemia (AML) and the potential for these master regulators to perturb normal hematopoiesis is well established. To date, overexpression of HOX genes in AML has been attributed to specific chromosomal aberrations and abnormalities involving mixed-lineage leukemia (MLL), an upstream regulator of HOX genes. The finding reported in this issue of the JCI by Scholl et al. that caudal-type homeobox transcription factor 2 (CDX2), which is capable of affecting HOX gene expression during embryogenesis, is overexpressed in 90% of patients with AML and induces a transplantable AML in murine models provides an alternative mechanism for HOX-induced leukemogenesis and yields important insights into the hierarchy of HOX gene regulation in AML (see the related article beginning on page 1037).
Kim L. Rice, Jonathan D. Licht
Although it was first described in 1989, our understanding of coenzyme Q10 (CoQ10) deficiency is only now coming of age with the recent first description of the underlying molecular defects. The diverse clinical presentations, classifiable into four major syndromes, raise the question as to whether the deficiencies are primary or secondary. Recent studies, including the one by Mollet, Rötig, and colleagues reported in this issue of the JCI, document molecular defects in three of the nine genes required for CoQ10 biosynthesis, all of which are associated with early and severe clinical presentations (see the related article beginning on page 765). It is anticipated that defects in the other six genes will cause similar early-onset encephalomyopathies. Awareness of CoQ10 deficiency is important because individuals with primary or secondary variants may benefit from oral CoQ10 supplementation.
Salvatore DiMauro, Catarina M. Quinzii, Michio Hirano
Protein accumulation is a hallmark of many neurodegenerative disorders. In Alzheimer’s disease (AD), a hyperphosphorylated form of the protein tau (p-tau) forms intracellular inclusions known as neurofibrillary tangles. Deposits of p-tau have also been found in the brains of patients with Down’s syndrome, supranuclear palsy, and prion disease. Mutations in tau have been causally associated with at least one inherited neurologic disorder, frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17), implying that tau abnormalities by themselves can be a primary cause of degenerative diseases of the CNS. Removal of these p-tau species may occur by both chaperone-mediated refolding and degradation. In this issue of the JCI, Dickey and colleagues show that a cochaperone protein, carboxyl terminus of Hsp70-interacting protein (CHIP), in a complex with Hsp90 plays an important role in the removal of p-tau (see the related article beginning on page 648). Pharmacologic manipulation of Hsp90 may be used to alleviate p-tau accumulation in disease.
Dmitry Goryunov, Ronald K.H. Liem
The hormone aldosterone increases extracellular fluid volume and blood pressure by activating epithelial Na+ channels (ENaCs). Serum- and glucocorticoid-induced kinase 1 (SGK1) is an aldosterone-stimulated signaling molecule that enhances distal nephron Na+ transport, in part by preventing the internalization of ENaCs from the plasma membrane. In this issue of the JCI, Zhang et al. demonstrate that SGK1 enhances transcription of the α subunit of ENaC by preventing histone methylation, providing an additional mechanism by which SGK1 increases ENaC-mediated Na+ transport in the distal nephron (see the related article beginning on page 773).
David Pearce, Thomas R. Kleyman
Inhaled environmental oxidants, such as ozone and particulates, have been variably linked to epithelial injury, inflammation, and perturbations in lung development, growth, and function. Reactions between ozone and lung surface lipids likely account for exposure-related pathophysiologic sequelae. In this issue of the JCI, Dahl et al. document a previously unrecognized pulmonary defense against inhaled oxidants in mice: macrophage scavenger receptors (SRs) bind proinflammatory oxidized lipids, thereby decreasing pulmonary inflammation (see the related article beginning on page 757). The study adds to our knowledge of diverse lung oxidative processes and identifies a potential regulatory mechanism governing pulmonary inflammation. Further investigations to elucidate more precise mechanisms and to determine the influence of SRs on airway epithelial injury, repair, and remodeling are warranted.
Edward M. Postlethwait
Natural antibodies are autoreactive/polyreactive antibodies believed to be secreted in the absence of xenoantigens. The origin and functional role of this limited and selective autoimmunity are not clear, nor is the specificity and range of autoantigens that drive the development of B cells producing natural antibodies. In this issue of the JCI, Merbl et al. report that in utero, humans generate natural IgM and IgA antibodies that recognize a uniform set of autoantigens (see the related article beginning on page 712), some of which are associated with autoimmune diseases. The authors postulate that this “autoimmunity” at birth favors the emergence of autoimmune diseases in later life. We present a molecular basis for the limited and common repertoire of antibodies produced by fetal B cells, which may be distinct from the abnormalities in B cell development described in patients with autoimmune diseases.
Eric Meffre, Jane E. Salmon
In this issue of the JCI, Vaisar et al. studied the proteome of HDL (see the related article beginning on page 746). They reveal, quite unexpectedly, that HDL is enriched in several proteins involved in the complement cascade, as well as in a variety of protease inhibitors, supporting the concept that HDL plays a role in innate immunity and in the regulation of proteolytic cascades involved in inflammatory and coagulation processes. The protein makeup of HDL also appears to be altered in patients with coronary artery disease. HDL proteomics is in its infancy, and preliminary findings will need to be confirmed using standardized approaches in larger clinical samples. However, this approach promises to better elucidate the relationship of HDL to atherosclerosis and its complications and could eventually help in the development of biomarkers to predict the outcome of interventions that alter HDL levels and functions.
Muredach P. Reilly, Alan R. Tall
The combination of the induction of lymphopenia and vaccination and/or T cell transfer is garnering much attention for cancer treatment. Preclinical studies have shown that the induction of lymphopenia by chemotherapy or radiation can enhance the antitumor efficacy of several distinct, cell-based immunotherapeutic approaches. The mechanism(s) by which such enhancement is achieved are being intensively studied, yet there is much opportunity for improvement. The animal studies reported by Wrzesinski and colleagues in this issue of the JCI are a promising and timely step in this direction (see the related article beginning on page 492). The authors have evaluated both the effect of increasing the intensity of lymphodepletion and the influence of HSC transfer on the in vivo function of adoptively transferred CD8+ T cells. We discuss their results in light of the evolving field and their implications for advancing cell-based immunotherapies for cancer.
Claudio Anasetti, James J. Mulé
It has become increasingly obvious that the notion of a terminally differentiated cell is likely a simplified concept. Epithelial-mesenchymal transition (EMT), during which epithelial cells assume a mesenchymal phenotype, is a key event occurring during normal development and pathological processes. Multiple extracellular stimuli and transcriptional regulators can trigger EMT, but how such distinct signaling pathways orchestrate the complex cellular events that facilitate EMT is not well understood. In this issue of the JCI, Venkov et al. report on their examination of fibroblasts resulting from EMT and describe a novel protein-DNA complex that is essential for transcription of fibroblast-specific protein 1 (FSP1) and sufficient to induce early EMT events (see the related article beginning on page 482). Collectively, their results suggest that this complex is an important regulator of the EMT transcriptome.
Yingqi Teng, Michael Zeisberg, Raghu Kalluri
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