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.

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.

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.