Blood REVIEW ARTICLES

The role of B cells in the pathogenesis of graft-versus-host disease

Thu, 03 Dec 2009 09:02:28 PST

Allogeneic hematopoietic stem cell transplantation is an established treatment modality for malignant and nonmalignant hematologic diseases. Acute and chronic graft-versus-host diseases (GVHDs) are a major cause of morbidity and mortality after allogeneic stem cell transplantation. T cells have been identified as key players in the graft-versus-host reaction and, therefore, most established drugs used against GVHD target T cells. Despite our knowledge on the pathogenesis of the GVH reaction, success of established therapies for prevention and treatment of GHVD is unsatisfactory. Recently, animal and human studies demonstrated that B cells are involved in the immunopathophysiology of acute and chronic GVHD. Early phase clinical trials of B-cell depletion with rituximab have shown beneficial effects on both acute and chronic GVHD. This review summarizes the current experimental and clinical evidence for the involvement of B cells in the pathogenesis of acute and chronic GVHD and discusses the clinical implications for the management of patients undergoing allogeneic stem cell transplantation.

Chronic lymphocytic leukemia: interplay between noncoding RNAs and protein-coding genes

Calin, G. A., Croce, C. M. — Thu, 26 Nov 2009 09:01:59 PST

One of the most unexpected and fascinating discoveries in oncology over the past few years is the interplay between abnormalities in protein-coding genes and noncoding RNAs (ncRNAs) that is causally involved in cancer initiation, progression, and dissemination. MicroRNAs (miRNAs), small regulatory ncRNAs, are involved in the pathogenesis of all types of human cancers, including leukemias, mainly via dysregulation of expression of cancer genes. Increasing evidence shows that miRNAs can work as tumor suppressors (inhibiting malignant potential) or oncogenes (activating malignant potential). Researchers first identified this new paradigm of molecular oncology in patients with chronic lymphocytic leukemia (CLL). Understanding the roles of miRNAs and other ncRNAs in leukemic cells is not only uncovering a new layer of gene regulation but also providing new markers for improved diagnosis and prognosis, as well as novel therapeutic options for CLL patients. Herein we focus on the roles of miRNAs and ultraconserved ncRNA genes in CLL, highlighting what is already known about their function, proposing a novel model of CLL predisposition and progression, and describing the challenges for the near future.

Mechanisms underlying neutrophil-mediated monocyte recruitment

Soehnlein, O., Lindbom, L., Weber, C. — Thu, 19 Nov 2009 09:02:19 PST

Extravasation of polymorphonuclear leukocytes (PMNs) to the site of inflammation precedes a second wave of emigrating monocytes. That these events are causally connected has been established a long time ago. However, we are now just beginning to understand the molecular mechanisms underlying this cellular switch, which has become even more complex considering the emergence of monocyte subsets, which are affected differently by signals generated from PMNs. PMN granule proteins induce adhesion as well as emigration of inflammatory monocytes to the site of inflammation involving β₂-integrins and formyl-peptide receptors. Furthermore, modification of the chemokine network by PMNs and their granule proteins creates a milieu favoring extravasation of inflammatory monocytes. Finally, emigrated PMNs rapidly undergo apoptosis, leading to the discharge of lysophosphatidylcholine, which attracts monocytes via G2A receptors. The net effect of these mechanisms is the accumulation of inflammatory monocytes, thus promoting proinflammatory events, such as release of inflammation-sustaining cytokines and reactive oxygen species. As targeting PMNs without causing serious side effects seems futile, it may be more promising to aim at interfering with subsequent PMN-driven proinflammatory events.

Acute graft-versus-host disease: from the bench to the bedside

Socie, G., Blazar, B. R. — Thu, 12 Nov 2009 09:38:04 PST

During the past decade, progress in basic immunology has been impressive. In parallel, whereas our understanding of the pathophysiology of acute graft-versus-host disease (GVHD) has greatly improved, so has our knowledge of the complexities of the immune system. Much of the immunobiology of acute GVHD has been gleaned from preclinical models and far less from correlations with clinical observations or therapeutic interventions. In this review, we summarize some of the major advances in GVHD pathophysiology, including the translation of these from the bench to the bedside, and discuss preclinical approaches that warrant further exploration in the clinic.