CD4(+) T helper (Th) lymphocytes represent a heterogeneous population of cells. In addition to type 1 (Th1) and type 2 (Th2) cells, another subset of CD4(+) effector Th cells has been discovered and named as Th17, because of its unique ability to produce interleukin (IL)-17. Studies in mice initially suggested that Th17 cells are the pathogenic cells in autoimmune disorders, whereas Th1 cells may behave rather as protective. Subsequent studies in humans demonstrated the plasticity of Th17 cells and their possibility to shift to Th1. The plasticity of Th17 to Th1 cells has recently been confirmed in mice, where it was found that Th17 cells seem to be pathogenic only when they shift to Th1 cells. Studies in humans also showed that Th17 cells are different than in mice because all of them express CD161 and exclusively originate from CD161(+) precursors present in umbilical cord blood and newborn thymus. While murine Th17 cells develop in response to IL-6, IL-1, and transforming growth factor (TGF)-beta, human Th17 cells originate from these CD161(+) precursors in response to IL-1beta and IL-23, the need for TGF-beta being controversial. Thus, we believe that studies in humans have better depicted human Th17 cells than studies in mice.

Recent multicenter studies have clarified the molecular basis underlying the different von Willebrand disease (VWD) types, all of which are caused by the deficiency and/or abnormality of von Willebrand factor (VWF). These studies have suggested a unifying pathophysiologic concept. The diagnosis of VWD, remains difficult because its clinical and laboratory phenotype is very heterogeneous and may overlap with normal subjects. Stringent criteria are therefore required for a clinically useful diagnosis. In this paper, we delineate a practical approach to the diagnosis and treatment of VWD. Our approach is based on the critical importance of a standardized bleeding history that has been condensed into a final bleeding score and a few widely available laboratory tests, such as VWF ristocetin cofactor activity, VWF antigen and factor VIII. This approach would help identify those subjects who will probably benefit from a diagnosis of VWD. The next step involves performing a trial infusion with desmopressin in all patients who fail to exhibit an enhanced responsiveness to ristocetin. On the basis of these results and through a series of illustrative examples, the clinician will be able to select the best approach for the optimal management of VWD, according to the patient's characteristics and clinical circumstances.

Effective gene therapy requires robust delivery of the desired genes into the relevant target cells, long-term gene expression, and minimal risks of secondary effects. The development of efficient and safe nonviral vectors would greatly facilitate clinical gene therapy studies. However, nonviral gene transfer approaches typically result in only limited stable gene transfer efficiencies in most primary cells. The use of nonviral gene delivery approaches in conjunction with the latest generation transposon technology based on Sleeping Beauty (SB) or piggyBac transposons may potentially overcome some of these limitations. In particular, a large-scale genetic screen in mammalian cells yielded a novel hyperactive SB transposase, resulting in robust and stable gene marking in vivo after hematopoietic reconstitution with CD34(+) hematopoietic stem/progenitor cells in mouse models. Moreover, the first-in-man clinical trial has recently been approved to use redirected T cells engineered with SB for gene therapy of B-cell lymphoma. Finally, induced pluripotent stem cells could be generated after genetic reprogramming with piggyBac transposons encoding reprogramming factors. These recent developments underscore the emerging potential of transposons in gene therapy applications and induced pluripotent stem generation for regenerative medicine.

Already 20 years have passed since the cloning of the granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor alpha-chain, the first member of the GM-CSF/interleukin (IL)-3/IL-5 family of hemopoietic cytokine receptors to be molecularly characterized. The intervening 2 decades have uncovered a plethora of biologic functions transduced by the GM-CSF receptor (pleiotropy) and revealed distinct signaling networks that couple the receptor to biologic outcomes. Unlike other hemopoietin receptors, the GM-CSF receptor has a significant nonredundant role in myeloid hematologic malignancies, macrophage-mediated acute and chronic inflammation, pulmonary homeostasis, and allergic disease. The molecular mechanisms underlying GM-CSF receptor activation have recently been revealed by the crystal structure of the GM-CSF receptor complexed to GM-CSF, which shows an unexpected higher order assembly. Emerging evidence also suggests the existence of intracellular signosomes that are recruited in a concentration-dependent fashion to selectively control cell survival, proliferation, and differentiation by GM-CSF. These findings begin to unravel the mystery of cytokine receptor pleiotropy and are likely to also apply to the related IL-3 and IL-5 receptors as well as other heterodimeric cytokine receptors. The new insights in GM-CSF receptor activation have clinical significance as the structural and signaling nuances can be harnessed for the development of new treatments for malignant and inflammatory diseases.

Over the past 20 years the molecular bases of almost all the major blood group antigens have been determined. This research has enabled development of DNA-based methods for determining blood group genotype. The most notable application of these DNA-based methods has been for determining fetal blood group in pregnancies when the fetus is at risk for hemolytic disease of the fetus and newborn. The replacement of all conventional serologic methods for pretransfusion testing by molecular methods is not straightforward. For the majority of transfusion recipients matching beyond ABO and D type is unnecessary, and the minority of untransfused patients at risk of alloimmunization who would benefit from more extensively blood group-matched blood cannot be identified reliably. Even if a method to identify persons most likely to make alloantibodies were available, this would not of itself guarantee the provision of extensively phenotype-matched blood for these patients because this is determined by the size and racial composition of blood donations available for transfusion. However, routine use of DNA-based extended phenotyping to provide optimally matched donations for patients with preexisting antibodies or patients with a known predisposition to alloimmunization, such as those with sickle cell disease, is widely used.

The genetic events that contribute to the pathogenesis of acute myeloid leukemia are among the best characterized of all human malignancies. However, with notable exceptions such as acute promyelocytic leukemia, significant improvements in outcome based on these insights have not been forthcoming. Acute myeloid leukemia is a paradigm of cancer stem (or leukemia initiating) cells with hierarchy analogous to that seen in hematopoiesis. Normal hematopoiesis requires complex bidirectional interactions between the bone marrow microenvironment (or niche) and hematopoietic stem cells (HSCs). These interactions are critical for the maintenance of normal HSC quiescence and perturbations can influence HSC self-renewal. Leukemia stem cells (LSCs), which also possess limitless self-renewal, may hijack these homeostatic mechanisms, take refuge within the sanctuary of the niche during chemotherapy, and consequently contribute to eventual disease relapse. We will discuss the emerging evidence supporting the importance of the bone marrow microenvironment in LSC survival and consider the physiologic interactions of HSCs and the niche that inform our understanding of microenvironment support of LSCs. Finally, we will discuss approaches for the rational development of therapies that target the microenvironment.

Immune thrombocytopenia (ITP) is mediated by platelet autoantibodies that accelerate platelet destruction and inhibit their production. Most cases are considered idiopathic, whereas others are secondary to coexisting conditions. Insights from secondary forms suggest that the proclivity to develop platelet-reactive antibodies arises through diverse mechanisms. Variability in natural history and response to therapy suggests that primary ITP is also heterogeneous. Certain cases may be secondary to persistent, sometimes inapparent, infections, accompanied by coexisting antibodies that influence outcome. Alternatively, underlying immune deficiencies may emerge. In addition, environmental and genetic factors may impact platelet turnover, propensity to bleed, and response to ITP-directed therapy. We review the pathophysiology of several common secondary forms of ITP. We suggest that primary ITP is also best thought of as an autoimmune syndrome. Better understanding of pathogenesis and tolerance checkpoint defects leading to autoantibody formation may facilitate patient-specific approaches to diagnosis and management.

Haptoglobin, the haptoglobin-hemoglobin receptor CD163, and the heme oxygenase-1 are proteins with a well-established function in the clearance and metabolism of "free" hemoglobin released during intravascular hemolysis. This scavenging system counteracts the potentially harmful oxidative and NO-scavenging effects associated with "free" hemoglobin, and, furthermore, elicits an anti-inflammatory response. In the late primate evolution, haptoglobin variants with distinct functions have arisen, including haptoglobin polymers and the haptoglobin-related protein. The latter associates with a subspecies of high-density lipoprotein (HDL) particles playing a crucial role in the innate immunity against certain trypanosome parasites. Recent studies have elucidated this fairly sophisticated immune defense mechanism that takes advantage of a trypanosomal haptoglobin-hemoglobin receptor evolved to supply the parasite with heme. Because of the high resemblance between haptoglobin and haptoglobin-related protein, the receptor also takes up the complex of hemoglobin and the HDL-bound haptoglobin-related protein. This tricks the parasite into internalizing another HDL-associated protein and toxin, apolipoprotein L-I, that kills the parasite. In conclusion, variant human homologous hemoglobin-binding proteins that collectively may be designated the haptoglobins have diverted from the haptoglobin gene. On hemoglobin and receptor interaction, these haptoglobins contribute to different biologic events that go beyond simple removal from plasma of the toxic hemoglobin.

Lymphomas of the ocular adnexa are a heterogeneous group of malignancies, composing approximately 1% to 2% of non-Hodgkin lymphomas (NHLs) and 8% of extranodal lymphomas. The most common subtype, accounting for up to 80% of cases of primary ocular adnexal lymphoma, is marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) type. In the recent past, there have been significant advances in our understanding of the clinical characteristics, morphology and phenotype, etiology, pathogenesis, diagnosis, natural history, treatment approaches, outcome, and prognostic factors of this disease entity. Novel immunologic and molecular techniques have aided in the distinction between MALT lymphoma and other lymphoproliferative disorders and led to the identification of tissue markers of prognostic significance. Modern imaging modalities provide invaluable tools for accurate staging and treatment planning. Besides radiotherapy and chemotherapy, a variety of new treatment options have emerged in the management of patients with ocular adnexal MALT lymphoma, especially monoclonal antibody therapy and antibiotic therapy against Chlamydia psittaci, which has been associated with the pathogenesis of ocular adnexal lymphomas in some parts of the world. In this review, we present a state-of-the-art summary of ocular adnexal MALT lymphomas.

Data from the Italian Hemophilia Centres were collected to perform a retrospective survey of joint arthroplasty in patients with severe hemophilia. Twenty-nine of 49 hemophilia centers reported that 328 of the 347 operations were carried out in 253 patients with severe hemophilia A (HA) and 19 in 15 patients with severe hemophilia B (HB). When results were normalized to the whole Italian hemophilia population (1770 severe HA and 319 severe HB), patients with HA had a 3-fold higher risk of undergoing joint arthroplasty (odds ratio [OR], 3.38; 95% confidence interval [CI], 1.97-5.77; P < .001). These results were confirmed after adjustment for age, HIV, hepatitis C virus (HCV), and inhibitor in a Cox regression model (HR, 2.65; 95% CI, 1.62-4.33; P < .001). The survival analysis of time to joint arthroplasty in the subset of patients with severe HA was not affected by the severity of factor VIII (FVIII) gene mutations. A systematic review of literature articles reporting joint arthroplasties in HA and HB showed that the proportion of HA patients who had undergone arthroplasties was higher than that of HB patients, in agreement with the findings in our Italian cohort. These data suggest that the 2 inherited coagulation disorders have a different severity of clinical phenotype.

Recently the World Health Organization (WHO), in collaboration with the European Association for Haematopathology and the Society for Hematopathology, published a revised and updated edition of the WHO Classification of Tumors of the Hematopoietic and Lymphoid Tissues. The 4th edition of the WHO classification incorporates new information that has emerged from scientific and clinical studies in the interval since the publication of the 3rd edition in 2001, and includes new criteria for the recognition of some previously described neoplasms as well as clarification and refinement of the defining criteria for others. It also adds entities-some defined principally by genetic features-that have only recently been characterized. In this paper, the classification of myeloid neoplasms and acute leukemia is highlighted with the aim of familiarizing hematologists, clinical scientists, and hematopathologists not only with the major changes in the classification but also with the rationale for those changes.

Wiskott-Aldrich syndrome (WAS) is a severe X-linked immunodeficiency caused by mutations in the gene encoding for WASP, a key regulator of signaling and cytoskeletal reorganization in hematopoietic cells. Mutations in WASP result in a wide spectrum of clinical manifestations ranging from the relatively mild X-linked thrombocytopenia to the classic full-blown WAS phenotype characterized by thrombocytopenia, immunodeficiency, eczema, and high susceptibility to developing tumors and autoimmune manifestations. The life expectancy of patients affected by severe WAS is reduced, unless they are successfully cured by bone marrow transplantation from related identical or matched unrelated donors. Because many patients lack a compatible bone marrow donor, the administration of WAS gene-corrected autologous hematopoietic stem cells could represent an alternative therapeutic approach. In the present review, we focus on recent progress in understanding the molecular and cellular mechanisms contributing to the pathophysiology of WAS. Although molecular and cellular studies have extensively analyzed the mechanisms leading to defects in T, B, and dendritic cells, the basis of autoimmunity and thrombocytopenia still remains poorly understood. A full understanding of these mechanisms is still needed to further implement new therapeutic strategies for this peculiar immunodeficiency.

High-dose therapy with allogeneic hematopoietic cell transplantation (HCT) offers effective control and potential cure of hematopoietic malignancies, but with the cost of associated morbidity that includes adverse effects on quality of life (QOL). A growing body of literature has characterized this impact. Longitudinal studies suggest early moderate impairments that largely return to pretransplantation levels by day 100; the majority of studies suggest that greater than 60% of patients report good to excellent QOL in years 1 to 4 after HCT. Comparisons of allogeneic HCT with autologous HCT and standard-dose chemotherapy suggest impairments in QOL and a different trajectory of recovery in allogeneic HCT, but these conclusions are limited by confounding variables. Cross-sectional studies suggest larger and more persistent decrements in QOL in comparison with matched noncancer controls and population normative data. Acute and chronic graft-versus-host disease (GVHD) are significant threats to QOL. Behavioral interventions show promise to maintain or improve quality of life after allogeneic HCT. The review concludes with recommendations to investigators and clinicians as the state of this research advances.

Managing patients with myelofibrosis (MF), either those with primary MF or those whose MF has evolved from antecedent polycythemia vera or essential thrombocythemia, presents many challenges to the hematologist. MF patients have a range of debilitating disease manifestations (eg, massive splenomegaly, cytopenias, constitutional symptoms, and transformation to a treatment-refractory blast phase). Cure is potentially achievable through allogeneic stem cell transplantation; however, this therapy is either inappropriate or not feasible for the majority of patients. Therefore, remaining therapies are palliative but can be of significant value to some MF patients. In particular, management of symptomatic splenomegaly remains one of the most perplexing aspects of MF clinical care. Using medications is the simplest approach for reducing splenomegaly, yet achieving symptomatic response without undue myelosuppression is challenging. Splenectomy or radiotherapy offers benefit, but careful patient selection and close monitoring are required because both have the potential for dangerous adverse effects. Experimental medical therapies, such as JAK2 inhibitors, show promise and may soon play an important role in the management of symptomatic splenomegaly in MF patients. Future care of MF patients, including splenomegaly management, will continue to require the hematologist to select therapeutic options carefully in the context of realistic, achievable goals.

von Willebrand factor (VWF) is a large multimeric adhesive glycoprotein with complex roles in thrombosis and hemostasis. Abnormalities in VWF give rise to a variety of bleeding complications, known as von Willebrand disease (VWD), the most common inherited bleeding disorder in humans. Current treatment of VWD is based on the replacement of the deficient or dysfunctional protein either by endogenous release from endothelial Weibel-Palade bodies or by administration of plasma-derived VWF concentrates. During the last years, several efforts have been made to optimize existing therapies for VWD, but also to devise new approaches, such as inducing endogenous expression with interleukin-11, administering exogenous recombinant VWF, or introducing the protein via gene delivery. Clearly, the efficacy of any strategy will depend on several factors, including, for example, the quantity, activity, and stability of the delivered VWF. The inherent complexity of VWF biosynthesis, which involves extensive posttranslational processing, may be limiting in terms of producing active VWF outside of its native cellular sources. This review summarizes recent progress in the development of different treatment strategies for VWD, including those that are established and those that are at the experimental stage. Potential pitfalls and benefits of each strategy are discussed.

Cytomegalovirus (CMV) continues to cause major complications after hematopoietic cell transplantation (HCT). Over the past decade, most centers have adopted preemptive antiviral treatment or prophylaxis strategies to prevent CMV disease. Both strategies are effective but also have shortcomings with presently available drugs. Here, we review aspects of CMV treatment and prevention in HCT recipients, including currently used drugs and diagnostics, ways to optimize preemptive therapy strategies with quantitative polymerase chain reaction assays, the use of prophylaxis, management of CMV disease caused by wild-type or drug-resistant strains, and future strategies.

Treatment of hematologic malignancies is evolving from a uniform approach to targeted therapies directed at the underlying molecular abnormalities of disease. The mixed lineage leukemia (MLL) proto-oncogene is a recurrent site of genetic rearrangements in acute leukemias; and since its discovery in 1992, many advances have been made in understanding its role in leukemogenesis. A variety of MLL translocation partners have been described, and detailed structure/function studies have identified functional domains that are required for transformation. Proteins associated with the MLL core complex or its fusion partners have been isolated and characterized for their critical roles in leukemia pathogenesis. Downstream mediators of MLL transcriptional regulation and multiple collaborating signaling pathways have been described and characterized. These advances in our understanding of MLL-related leukemogenesis provide a foundation for ongoing and future efforts to develop novel therapeutic strategies that will hopefully result in better treatment outcomes.

Dyskeratosis congenita (DC) is a rare inherited bone marrow failure syndrome. The spectrum of cancer susceptibility in this disorder of telomere biology has not been described. There were more than 500 cases of DC reported in the literature from 1910 to 2008; the National Cancer Institute (NCI) prospective DC cohort enrolled 50 cases from 2002 to 2007. Sixty cancers were reported in 52 literature cases, while 7 occurred among patients in the NCI DC cohort. The 2 cohorts were comparable in their median overall survival (42 years) and cumulative incidence of cancer (40%-50% by age 50 years). The most frequent solid tumors were head and neck squamous cell carcinomas (40% of patients in either cohort), followed by skin and anorectal cancer. The ratio of observed to expected cancers (O/E ratio) in the NCI cohort was 11-fold compared with the general population (P < .05). Significantly elevated O/E ratios were 1154 for tongue cancer and 195 for acute myeloid leukemia. Survival after bone marrow transplantation for aplastic anemia or leukemia was poor in both cohorts. The frequency and types of cancer in DC are surpassed only by those in Fanconi anemia (FA), indicating that FA and DC have similarly high risks of adverse hematologic and neoplastic events, and patients with these diseases should be counseled and monitored similarly.

European experts were convened to develop a definition of response to treatment in polycythemia vera (PV) and essential thrombocythemia (ET). Clinicohematologic (CH), molecular, and histologic response categories were selected. In ET, CH complete response (CR) was: platelet count less than or equal to 400 x 10(9)/L, no disease-related symptoms, normal spleen size, and white blood cell count less than or equal to 10 x 10(9)/L. Platelet count less than or equal to 600 x 10(9)/L or a decrease greater than 50% was partial response (PR). In PV, CH-CR was: hematocrit less than 45% without phlebotomy, platelet count less than or equal to 400 x 10(9)/L, white blood cell count less than or equal to 10 x 10(9)/L, and no disease-related symptoms. A hematocrit less than 45% without phlebotomy or response in 3 or more of the other criteria was defined as PR. In both ET and in PV, molecular CR was a reduction of any molecular abnormality to undetectable levels. Molecular PR was defined as a reduction more than or equal to 50% in patients with less than 50% mutant allele burden, or a reduction more than or equal to 25% in patients with more than 50% mutant allele burden. Bone marrow histologic response in ET was judged on megakaryocyte hyperplasia while on cellularity and reticulin fibrosis in PV. The combined use of these response definitions should help standardize the design and reporting of clinical studies.