Latent enhancers activated by stimulation in differentiated cells.

According to current models, once the cell has reached terminal differentiation, the enhancer repertoire is completely established and maintained by cooperatively acting lineage-specific transcription factors (TFs). TFs activated by extracellular stimuli operate within this predetermined repertoire, landing close to where master regulators are constitutively bound. Here, we describe latent enhancers, defined as regions of the genome that in terminally differentiated cells are unbound by TFs and lack the histone marks characteristic of enhancers but acquire these features in response to stimulation. Macrophage stimulation caused sequential binding of stimulus-activated and lineage-determining TFs to these regions, enabling deposition of enhancer marks. Once unveiled, many of these enhancers did not return to a latent state when stimulation ceased; instead, they persisted and mediated a faster and stronger response upon restimulation. We suggest that stimulus-specific expansion of the cis-regulatory repertoire provides an epigenomic memory of the exposure to environmental agents.

Coregulation of transcription factor binding and nucleosome occupancy through DNA features of mammalian enhancers.

Transcription factors (TFs) preferentially bind sites contained in regions of computationally predicted high nucleosomal occupancy, suggesting that nucleosomes are gatekeepers of TF binding sites. However, because of their complexity mammalian genomes contain millions of randomly occurring, unbound TF consensus binding sites. We hypothesized that the information controlling nucleosome assembly may coincide with the information that enables TFs to bind cis-regulatory elements while ignoring randomly occurring sites. Hence, nucleosomes would selectively mask genomic sites that can be contacted by TFs and thus be potentially functional. The hematopoietic pioneer TF Pu.1 maintained nucleosome depletion at macrophage-specific enhancers that displayed a broad range of nucleosome occupancy in other cell types and in reconstituted chromatin. We identified a minimal set of DNA sequence and shape features that accurately predicted both Pu.1 binding and nucleosome occupancy genome-wide. These data reveal a basic organizational principle of mammalian cis-regulatory elements whereby TF recruitment and nucleosome deposition are controlled by overlapping DNA sequence features.

Evaluation of the applicability and effectiveness of a molecular strategy for identifying weak D and DEL phenotype among D- blood donors of mixed origin exhibiting high frequency of RHD*Ψ.

BACKGROUND: Molecular tests designed to detect the presence of active RHD gene among D- donors have been successfully applied in people of European ancestry, but not in admixed populations with a considerable frequency of RHD*Ψ. Our goal was to evaluate the performance of a molecular screening tool for identifying active RHD alleles among Brazilian blood donors classified as D- C+ and/or E+. STUDY DESIGN AND METHODS: Pools of five DNA samples of serologically D- C+ and/or E+ donors were checked by a RHD polymerase chain reaction (PCR) assay specific for RHD Intron 4 and Exon 7. When a pool result was positive, samples were genotyped individually for RHD Intron 4 and Exon 7, RHD*Ψ, RHCE*Cc, and RHD zygosity. Donors suspected of active RHD gene were further evaluated by whole-coding region and flanking intron direct sequencing. RESULTS: A total of 405 donors were included. Two percent exhibited active RHD gene, codifying D-weak (38 and 45) or DEL phenotype. The most prevalent DEL allele was RHD*DEL1 (c.1227G>A), which is proven to be immunogenic. A high frequency of RHD*Ψ was detected in the donors with nondeleted RHD alleles (31%), far superior to the frequency of RHD variant alleles (15.5%). The proposed approach presented sensitivity of 100% and specificity of 85.7% for identifying active RHD gene. CONCLUSION: The strategy of checking D- donors with RHD PCR followed by exclusion of RHD*Ψ allele has proved efficient in identifying weak-D and DEL phenotype in the Brazilian population.

High frequency of variant RHD genotypes among donors and patients of mixed origin with serologic weak-D phenotype.

BACKGROUND: The current transfusion policy recommended for individuals with serologic weak-D phenotype is based on data derived from European-descent populations. Data referring to the distribution of RH alleles underlying weak-D phenotype among people of mixed origin are yet incomplete, and the applicability of European-based transfusion guidelines to this specific population is questionable. GOAL: To evaluate the distribution of RHD variant genotype among individuals with serologic weak-D phenotype of both African and European descent. METHODS: Donors and patients of mixed origin and with serologic weak-D phenotype were selected for the study. They were investigated using conventional RHD-PCR assays and RHD whole-coding region direct sequencing. RESULTS: One hundred and six donors and 58 patients were included. There were 47 donors and 29 patients with partial-D genotype (47/106, 44.3%, and 29/58, 50%, respectively). RHD*DAR and RHD*weak D type 38 represented the most common altered RHD alleles among donors (joint frequency of 39.6%), while weak D types 1-3 accounted for 10.4% of the total D variant samples. RHD*DAR was the most common allele identified in the patient group (frequency of 31%), and weak D types 1-3 represented 29.3% of the total. CONCLUSION: The frequency of partial D among mixed individuals with serologic weak-D phenotype is high. They should be managed as D-negative patients until molecular tests are complete.

Defining the clinical relevance of red blood cell autoantibodies by Monocyte Monolayer Assay.

BACKGROUND: The Monocyte Monolayer Assay (MMA) is an in vitro simulation of red blood cell (RBC) alloantibody behavior. It has been classically applied to predict the risks of post-transfusion hemolytic reactions when transfusing incompatible RBC units. Quantifying erythrophagocytosis by MMA may be an interesting option for situations where there is doubt whether a RBC autoantibody is mediating significant hemolysis. Here, we present three situations involving RBC autoantibodies in which the MMA was decisive for clarifying the diagnosis and choosing the best clinical treatment. CASE REPORT: Case 1. Pregnant patient with severely anemic fetus exhibited warm autoantibody without signs of hemolysis. MMA revealed 30% of monocyte index (MI) highlighting that fetal hemolysis was caused by maternal autoantibody. Prednisone was prescribed with fetal clinical improvement. Cases 2 and 3. Two patients with the diagnosis of mixed auto-immune hemolytic anemia and poor response to corticosteroids were evaluated using MMA. The resulting MI was less than 10% in both cases, suggesting that the cold-agglutinin rather than the warm auto-IgG was responsible for overt hemolysis. Treatment with rituximab was begun, with good clinical response. CONCLUSION: MMA can be used to evaluate the ability of RBC autoantibodies to mediate overt hemolysis. It can be especially useful to determine the role played by cold and warm auto-antibodies in mixed auto-immune hemolytic disease, helping to define the best treatment option.

Non-peptidic thrombospondin-1 mimics as fibroblast growth factor-2 inhibitors: an integrated strategy for the development of new antiangiogenic compounds.

Endogenous inhibitors of angiogenesis, such as thrombospondin-1 (TSP-1), are promising sources of therapeutic agents to treat angiogenesis-driven diseases, including cancer. TSP-1 regulates angiogenesis through different mechanisms, including binding and sequestration of the angiogenic factor fibroblast growth factor-2 (FGF-2), through a site located in the calcium binding type III repeats. We hypothesized that the FGF-2 binding sequence of TSP-1 might serve as a template for the development of inhibitors of angiogenesis. Using a peptide array approach followed by binding assays with synthetic peptides and recombinant proteins, we identified a FGF-2 binding sequence of TSP-1 in the 15-mer sequence DDDDDNDKIPDDRDN. Molecular dynamics simulations, taking the full flexibility of the ligand and receptor into account, and nuclear magnetic resonance identified the relevant residues and conformational determinants for the peptide-FGF interaction. This information was translated into a pharmacophore model used to screen the NCI2003 small molecule databases, leading to the identification of three small molecules that bound FGF-2 with affinity in the submicromolar range. The lead compounds inhibited FGF-2-induced endothelial cell proliferation in vitro and affected angiogenesis induced by FGF-2 in the chicken chorioallantoic membrane assay. These small molecules, therefore, represent promising leads for the development of antiangiogenic agents. Altogether, this study demonstrates that new biological insights obtained by integrated multidisciplinary approaches can be used to develop small molecule mimics of endogenous proteins as therapeutic agents.

Transfusion of ABO non-identical platelets increases the severity of trauma patients at ICU admission.

BACKGROUND: Transfusion of ABO-compatible non-identical platelets (PTLs), fresh plasma (FP) and red blood cells (RBCs) has been associated with increased morbidity and mortality of recipients. Trauma victims are frequently exposed to ABO non-identical products, given the need for emergency transfusions. Our goal was to evaluate the impact of the transfusion of ABO non-identical blood products on the severity and all-cause 30-day mortality of trauma patients. METHODS: This was a retrospective single-center cohort, which included trauma patients who received emergency transfusions in the first 24 h of hospitalization. Patients were divided in two groups according to the use of <3 or ≥3 ABO non-identical blood products. The patient severity, measured by the Acute Physiology and Chronic Health Evaluation (APACHEII) score at ICU admission, and the 30-day mortality were compared between groups. RESULTS: Two hundred and sixteen trauma patients were enrolled. Of these, 21.3% received ≥3 ABO non-identical blood products (RBCs, PLTs and FP or cryoprecipitate). The transfusion of ≥3 ABO non-identical blood products in the first 24 h of hospitalization was independently associated with a higher APACHEII score at ICU admission (OR = 3.28 and CI95% = 1.48-7.16). Transfusion of at least one unit of ABO non-identical PTLs was also associated with severity (OR = 10.89 and CI95% = 3.38-38.49). Transfusion of ABO non-identical blood products was not associated with a higher 30-day mortality in the studied cohort. CONCLUSION: The transfusion of ABO non-identical blood products and, especially, of ABO non-identical PLTs may be associated with the greater severity of trauma patients at ICU admission. The transfusion of ABO non-identical blood products in the trauma setting is not without risks.

Transfusion of ABO non-identical platelets increases the severity of trauma patients at ICU admission

ABSTRACT Background: Transfusion of ABO-compatible non-identical platelets (PTLs), fresh plasma (FP) and red blood cells (RBCs) has been associated with increased morbidity and mortality of recipients. Trauma victims are frequently exposed to ABO non-identical products, given the need for emergency transfusions. Our goal was to evaluate the impact of the transfusion of ABO non-identical blood products on the severity and all-cause 30-day mortality of trauma patients. Methods: This was a retrospective single-center cohort, which included trauma patients who received emergency transfusions in the first 24 h of hospitalization. Patients were divided in two groups according to the use of <3 or ≥3 ABO non-identical blood products. The patient severity, measured by the Acute Physiology and Chronic Health Evaluation (APACHEII) score at ICU admission, and the 30-day mortality were compared between groups. Results: Two hundred and sixteen trauma patients were enrolled. Of these, 21.3% received ≥3 ABO non-identical blood products (RBCs, PLTs and FP or cryoprecipitate). The transfusion of ≥3 ABO non-identical blood products in the first 24 h of hospitalization was independently associated with a higher APACHEII score at ICU admission (OR = 3.28 and CI95% = 1.48-7.16). Transfusion of at least one unit of ABO non-identical PTLs was also associated with severity (OR = 10.89 and CI95% = 3.38-38.49). Transfusion of ABO non-identical blood products was not associated with a higher 30-day mortality in the studied cohort. Conclusion: The transfusion of ABO non-identical blood products and, especially, of ABO non-identical PLTs may be associated with the greater severity of trauma patients at ICU admission. The transfusion of ABO non-identical blood products in the trauma setting is not without risks.

Thrombospondin-1 as a Paradigm for the Development of Antiangiogenic Agents Endowed with Multiple Mechanisms of Action.

Uncontrolled neovascularization occurs in several angiogenesis-dependent diseases, including cancer. Neovascularization is tightly controlled by the balance between angiogenic growth factors and antiangiogenic agents. The various natural angiogenesis inhibitors identified so far affect neovascularization by different mechanisms of action. Thrombospondin-1 (TSP-1) is a matricellular modular glycoprotein that acts as a powerful endogenous inhibitor of angiogenesis. It acts both indirectly, by sequestering angiogenic growth factors and effectors in the extracellular environment, and directly, by inducing an antiangiogenic program in endothelial cells following engagement of specific receptors including CD36, CD47, integrins and proteoglycans (all involved in angiogenesis ). In view of its central, multifaceted role in angiogenesis, TSP-1 has served as a source of antiangiogenic tools, including TSP-1 fragments, synthetic peptides and peptidomimetics, gene therapy strategies, and agents that up-regulate TSP-1 expression. This review discusses TSP-1-based inhibitors of angiogenesis, their mechanisms of action and therapeutic potential, drawing our experience with angiogenic growth factor-interacting TSP-1 peptides, and the possibility of exploiting them to design novel antiangiogenic agents.

Funções biológicas dos antígenos eritrocitários: [revisão] / Biological functions of blood group antigens: [review]

Os antígenos de grupos sanguíneos eritrocitários são estruturas macromoleculares localizadas na superfície extracelular da membrana eritrocitária. Com o desenvolvimento de estudos moleculares, mais de 250 antígenos são conhecidos e estão organizados em 29 sistemas de grupos sanguíneos reconhecidos pela Sociedade Internacional de Transfusão Sanguínea (ISBT). Estudos têm revelado que os antígenos de grupo sanguíneo estão expressos na membrana eritrocitária com ampla diversidade estrutural, incluindo epítopos de carboidratos em glicoproteínas e/ou glicolipídios e em proteínas inseridas na membrana via um domínio, via domínios de multipassagem ou ligados a glicosilfosfatidinositol. Além das diversidades estruturais, muitas funções importantes têm sido associadas aos antígenos eritrocitários recentemente identificadas, podendo ser esquematicamente divididas em: estruturais, transportadores, receptores e moléculas de adesão, enzimas, proteínas controladoras do complemento e outras. Esta revisão tem como foco as funções potenciais das moléculas que expressam os antígenos eritrocitários.

Erythrocyte blood group antigens are macromolecules structures located on the extracellular surface of the red blood cell membrane. The development of molecular studies allowed the recognition of more than 250 antigens by the International Society for Blood Transfusion (ISBT). These studies have also shown that blood group antigens are carried on red blood cell membrane of wide structural diversity, including carbohydrate epitopes on glycoproteins and/or glycolipids and on proteins inserted within the membrane via single or multi-pass transmembrane domains, or via glycosylphosphatidylinositol linkages. In addition, to their structural diversity, many important functions associated with blood group antigens have been recently identified and can be didactically divided into: structural proteins, transporters, receptors and adhesion molecules, enzymes, complement control proteins and others. This review will focus on the potential functions of the molecules that express blood group antigens.

Dez anos de experiência em controle de qualidade em imuno-hematologia / Ten years of experience of quality control in immunohematology

A medicina transfusional tem como objetivo garantir a qualidade e quantidade do sangue, componentes e serviços oferecidos à comunidade, e, dentro desse contexto, a análise dos reagentes imuno-hematológicos é crítica para a realização dos testes pré-transfusionais e, consequentemente, uma transfusão segura. É responsabilidade do controle de qualidade o constante aperfeiçoamento de testes que analisam a qualidade dos reagentes e equipamentos utilizados. Esse trabalho tem por objetivo apresentar os resultados alcançados em dez anos de experiência do Departamento de Controle de Qualidade em Imuno-hematologia da Fundação Pró-Sangue / Hemocentro de São Paulo. No período de janeiro de 1997 a dezembro de 2007 foram realizadas análises em 3.417 reagentes imuno-hematológicos por ocasião da aquisição do reagente e por solicitação de reavaliação (durante o uso). As análises incluíram desde a inspeção visual no recebimento a testes laboratoriais específicos para cada tipo de reagente. Dos 3.417 lotes analisados (média=310/ano, mediana=252/ano), 94 (2,7 por cento) foram reprovados (média=8,54/ano, mediana=7,00 ± 7,79/ano). Uma vez aprovado pelo controle de qualidade à aquisição, nenhum reagente imunohematológico foi reprovado durante o uso desde 2004. Podemos concluir que, para implementação de um sistema de controle de qualidade de reagentes imuno-hematológicos, não é necessário uso de reagentes ou equipamentos altamente especializados, pois os mesmos são utilizados na rotina laboratorial, como também não envolvem alta complexidade na execução das análises. Podemos enfim considerar que a implementação do controle de qualidade em Imuno-hematologia contribui para o aumento da segurança transfusional e é factível de realização nos mais diferentes níveis de complexidade dos serviços hemoterápicos.

Transfusion medicine has the purpose of guaranteeing the quality and quantity of blood, blood derivatives and services offered to the community. Thus, the analysis of serological reagents is critical in pre-transfusion testing and, consequently, reliable transfusions. A constant improvement in the tests that analyze the quality of reagents and equipment utilized is the responsibility of quality control. This paper aims at presenting the results and experience achieved over 10 years in the Department of Quality Control in Immunohematology at Fundação Pró-Sangue / Hemocentro de São Paulo. In the period of January 1997 to December 2007 we carried out analyses of 3,417 serological reagents at acquisition and/or during their use. The analyses included from visual inspection to specific laboratory tests for each kind of reagent. Of the 3,417 lots analyzed (mean = 310/year, median = 252/year), 94 (2.7 percent - median=8.54/year) failed the tests. From 2004 to date, once the reagents were approved, none failed during use. The implementation of a quality control system with standardized techniques is important for the adequate utilization of serological reagents. This system accomplished by retroactive control of the reagents, contributed to the safety and reliability of results in immunohematology testing.

Hemolytic disease of the newborn due to anti-U

Anti-U is a rare red blood cell alloantibody that has been found exclusively in blacks. It can cause hemolytic disease of the newborn and hemolytic transfusion reactions. We describe the case of a female newborn presenting a strongly positive direct antiglobulin test due to an IgG antibody in cord blood. Anti-U was recovered from cord blood using acid eluate technique. Her mother presented positive screening of antibodies with anti-U identified at delivery. It was of IgG1 and IgG3 subclasses and showed a titer of 32. Monocyte monolayer assay showed moderate interaction of Fc receptors with maternal serum with a positive result (3.1 percent). The newborn was treated only with 48 hours of phototherapy for mild hemolytic disease. She recovered well and was discharged on the 4th day of life. We conclude that whenever an antibody against a high frequency erythrocyte antigen is identified in brown and black pregnant women, anti-U must be investigated