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Alpha hemolysin (HlyA) is a hemolytic and cytotoxic protein secreted by uropathogenic strains of E. coli. The role of glycophorins (GPs) as putative receptors for HlyA binding to red blood cells (RBCs) has been debated. Experiments using anti-GPA/GPB antibodies and a GPA-specific epitope nanobody to block HlyA-GP binding on hRBCs, showed no effect on hemolytic activity. Similarly, the hemolysis induced by HlyA remained unaffected when hRBCs from a GPAnull/GPBnull variant were used. Surface Plasmon Resonance experiments revealed similar values of the dissociation constant between GPA and either HlyA, ProHlyA (inactive protoxin), HlyAΔ914-936 (mutant of HlyA lacking the binding domain to GPA) or human serum albumin, indicating that the binding between the proteins and GPA is not specific. Although far Western blot followed by mass spectroscopy analyses suggested that HlyA interacts with Band 3 and spectrins, hemolytic experiments on spectrin-depleted hRBCs and spherocytes, indicated these proteins do not mediate the hemolytic process. Our results unequivocally demonstrate that neither glycophorins, nor Band 3 and spectrins mediate the cytotoxic activity of HlyA on hRBCs, thereby challenging the HlyA-receptor hypothesis. This finding holds significant relevance for the design of anti-toxin therapeutic strategies, particularly in light of the growing antibiotic resistance exhibited by bacteria.

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OBJECTIVE: To evaluate laboratory indices in patients with hereditary spherocytosis, with positive and borderline flow cytometry eosin-5-melamide (EMA)-bound red blood cells screening test. STUDY DESIGN: We compared laboratory indices of 151 samples obtained from 139 different individual patients with negative, borderline, or positive EMA-test results. We also compared the clinical data of the patients in each EMA test results group. RESULTS: Borderline EMA-test results were obtained for 13 patients and were associated with more severe anemia, and lower reticulocyte count and reticulocyte production index compared with samples with positive EMA-test results. A receiving operator characteristic analysis identified mean corpuscular hemoglobin concentration of <32.5 g/dL as a cut-off, between positive/borderline and negative test results with 100% sensitivity. A higher prevalence of clinical markers typical of hereditary spherocytosis was found in patients with borderline or positive compared with negative EMA test samples. CONCLUSIONS: Based on laboratory data, borderline EMA-test results may be an indication of a more severe form of hereditary spherocytosis. Using mean corpuscular hemoglobin concentration as a cut-off may help predict and reduce negative EMA tests without compromising sensitivity. This finding needs to be further validated in other flow cytometry laboratories with a large EMA test sample pool.

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Painful vaso-occlusive crisis, a hallmark of sickle cell anaemia, results from complex, incompletely understood mechanisms. Red blood cell (RBC) damage caused by continuous endogenous and exogenous oxidative stress may precipitate the occurrence of vaso-occlusive crises. In order to gain insight into the relevance of oxidative stress in vaso-occlusive crisis occurrence, we prospectively compared the expression levels of various oxidative markers in 32 adults with sickle cell anaemia during vaso-occlusive crisis and steady-state conditions. Compared to steady-state condition, plasma levels of free haem, advanced oxidation protein products and myeloperoxidase, RBC caspase-3 activity, as well as the concentrations of total, neutrophil- and RBC-derived microparticles were increased during vaso-occlusive crises, whereas the reduced glutathione content was decreased in RBCs. In addition, natural anti-band 3 autoantibodies levels decreased during crisis and were negatively correlated with the rise in plasma advanced oxidation protein products and RBC caspase-3 activity. These data showed an exacerbation of the oxidative stress during vaso-occlusive crises in sickle cell anaemia patients and strongly suggest that the higher concentration of harmful circulating RBC-derived microparticles and the reduced anti-band 3 autoantibodies levels may be both related to the recruitment of oxidized band 3 into membrane aggregates.

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Introducción: Se ha demostrado la participación de moléculas de adhesión, tanto en eritrocitos con hemoglobina SS, como en el endotelio vascular; así como factores plasmáticos en el fenómeno de vasoclusión en la drepanocitosis. La banda 3 se refiere a una familia de intercambiadores aniónicos presentes en la membrana de todas las células y organelos celulares, las que bajo ciertas condiciones se agregan en la superficie del eritrocito y son reconocidos por anticuerpos naturales como parte del mecanismo de eliminación de eritrocitos senescentes u oxidados. Objetivo: Evaluar la posible participación de los anticuerpos naturales antibanda 3 en el fenómeno oclusivo en la drepanocitosis. Métodos: Se realizó la determinación seriada de anticuerpos naturales antibanda 3 en 19 enfermos con drepanocitosis en diferentes estadios clínicos mediante un ensayo inmunoenzimático en microplacas acopladas con la proteína banda 3. Resultados: Se demostró una disminución significativa (p < 0.01) de anticuerpos naturales antibanda 3 en las muestras de los enfermos obtenidas en las fases de crisis vasoclusiva dolorosa, disminución que pudiera estar relacionada con un consumo elevado de estos en el proceso de eliminación de eritrocitos SS oxidados de la circulación sanguínea. Las muestras en estado basal se mantuvieron dentro de los límites normales. Conclusión: Los resultados sugieren la participación de los anticuerpos naturales antibanda 3 como elemento regulador de la no adhesión de los eritrocitos SS al endotelio vascular en esta enfermedad(AU)

Introduction : The involvement of adhesion molecules in erythrocytes with hemoglobin SS, in vascular endothelium and also plasma factors have been shown in the vasoocclusion phenomenon in sickle cell anemia (SCA). Band 3 refers to a family of anion exchangers present in the membrane of all cells and cellular organelles which under certain conditions cluster on the erythrocyte surface being recognized by natural antibodies as part of the mechanism of removal of senescent or oxidized erythrocytes. Objective : To evaluate the possible participation of natural anti band 3 antibodies in the occlusive phenomenon in SCA. Methods : A follow up study to determine the presence of natural band 3 antibodies in 19 patients with SCA in different clinical stages was performed using an enzyme immunoassay in microplates coupled with the band 3 protein. Results : Significant low levels (p<0.01) of natural band 3 antibodies were demonstrated in the samples of patients obtained in painful vasoocclusive crisis stages, decrease which may be related to a high consumption of antibodies in the process of removing oxidized SS erythrocytes from blood circulation. Steady state samples were within normal range. Conclusion: The results suggest the involvement of natural band 3 antibodies in the regulation of the adherence of SS erythrocytes to vascular endothelium in SCA(AU)

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Chronic lymphocytic leukemia (CLL) is the main cause of autoimmune hemolytic anemia (AHA). However, the cellular basis underlying this strong association remains unclear. We previously demonstrated that leukemic B cells from patients with CLL recognize the erythrocyte protein Band 3, a prevalent autoantigen in AHA. Here we show that the major binding site of Band 3 on leukemic cells is an extrinsic protein identified as high-mobility group nucleosome binding protein 2 (HMGN2), a nucleosome-interacting factor which has not been previously reported at the cell surface. T lymphocytes do not express HMGN2 or bind Band 3. Removal of HMGN2 from the cell membrane abrogated the capacity of Band 3-pulsed CLL cells to induce CD4 + T cell proliferation. We conclude that surface HMGN2 in leukemic B cells is involved in Band 3 binding, uptake and presentation to CD4 + T lymphocytes, and as such may favor the initiation of AHA secondary to CLL.

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We analyzed the SLC4A1 gene in three Mexican patients with Hereditary Spherocytosis (HS). The promoter and all 20 exons were investigated through heteroduplex analysis and DNA sequencing. No DNA changes were detected in one of the three patients. Two well-known polymorphisms, Memphis I and the Diego-a blood group, were detected in another one. In the third, the HS phenotype could be explained by the novel 1885_1888dupCCGG mutation found in heterozygosis. This frameshift mutation is predicted to result in a truncated and unstable protein lacking normal functions.

RESUMO

We analyzed the SLC4A1 gene in three Mexican patients with Hereditary Spherocytosis (HS). The promoter and all 20 exons were investigated through heteroduplex analysis and DNA sequencing. No DNA changes were detected in one of the three patients. Two well-known polymorphisms, Memphis I and the Diego-a blood group, were detected in another one. In the third, the HS phenotype could be explained by the novel 1885_1888dupCCGG mutation found in heterozygosis. This frameshift mutation is predicted to result in a truncated and unstable protein lacking normal functions.

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La vaso-oclusión en la drepanocitosis es una característica única entre las anemias hemolíticas. La idea de que el eritrocito falciforme induce el proceso vaso-oclusivo ha sido desechada y no cabe duda que el fenómeno ocurre debido a la adhesión de los hematíes deformables menos densos (reticulocitos de stress) al endotelio vascular activado en las vénulas post-capilares, proceso en el que participan moléculas de adhesión celular (MAC) eritrocitarias y vasculares así como un conjunto de factores plasmáticos; la externalización de la fosfatidilserina, la acción de la trombina, la expresión de factor tisular asociada a alteraciones del mecanismo de transporte catiónico, conjuntamente con la formación de agregados de banda 3 constituyen un conjunto de elementos cruciales en la explicación fisiopatológica de la vaso-oclusión y su relación con diferentes opciones terapéuticas.

The vaso-occlusion in the sickle cell anemia is only characteristic in the haemolytic anemias. The idea that the falciform erythrocyte induces the vaso-occlusive process has been abolished and without doubt the event is produced by the adhesion of the low density deformed erythrocytes ( stress reticulocytes ) to the active vascular endothelium in post-capillary venule participating in the process molecules of cellular adhesion ( erythrocytic and vascular) as well as a group of plasma factors; the external phosphatidilserine , the thrombine action , the expression of tissue factor associated to the disorders of the cationic transportation mechanism as well as the aggregates (band 3) are crucial elements in the pathophysiological explanation of vaso-occlusion and its relation to different therapeutic options.

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Se determinó la presencia de anticuerpos naturales anti banda 3 mediante un ensayo inmunoenzimático en microplacas acopladas con la proteína banda 3 en 14 pacientes con drepanocitosis, 4 con crisis vasooclusiva dolorosa y 10 en estado basal. Se demostró una disminución significativa (p = 0,000005) de los niveles de los anticuerpos naturales anti banda 3 en el total de los pacientes al compararlos con los controles normales, lo que puede estar relacionado con un consumo elevado de estos en el proceso de aclaramiento de eritrocitos con hemoglobina SS oxidados o senescentes. No se demostró diferencia estadística entre el grupo de pacientes en estado basal y aquellos con crisis vasooclusiva dolorosa, lo cual sugiere la posibilidad de que no haya participación de los anticuerpos naturales anti banda 3 en la modulación del fenómeno oclusivo que se produce en esta enfermedad. Se recomienda el estudio longitudinal de un número mayor de pacientes, que permita profundizar en este aspecto.

The presence of natural anti-band 3 antibodies was determined by an immunoenzymatic assay in microplaques coupled with band 3 protein in 14 patients with drepanocytosis, 4 with painful vasoocclusive crisis and 10 in the basal state. It was proved a significant reduction (p = 0,000005) of the levels of natural anti-band 3 antibodies in all the patients on comparing them with the normal controls, which may be related to an elevated consumption of these in the clearance process of oxidized or senescent erythrocytes with hemoglobin SS. There was no statistical difference between the group of patients in the basal state and those with painful vasoocclusive crisis, which suggests that the natural anti-band 3 antibodies do not take part in the modulation of the occlusive phenomenon that is produced in this disease. The longitudinal study of a greater number of patients that allows to go deep into this apect is recommended.

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Se purifica la proteína banda 3 a partir de membranas de eritrocitos humanos con rapidez y eficiencia, mediante una combinación de cromatografía de intercambio iónico en DEAE-celulosa y de afinidad mediante el empleo de una columna pCMB-Sepharose. La obtención de banda 3 permitirá investigar su posible participación en los fenómenos oclusivos en la drepanocitosis.

The band 3 protein is purified starting form the membranes of human erythrocytes with celerity and efficiency by a combination of DEAE-cellulose ion-exchange and affinity chromatography by using a pCMB-Sepharose column. The obtention of band 3 will allow to investigate its possible participation in the occlusive phenomena in drepanocytosis.

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Se purificaron anticuerpos naturales anti banda 3 de la clase IgG mediante cromatografía de afinidad con un aceptable nivel de pureza, rapidez y eficiencia, a partir de una mezcla de inmunoglobulinas humanas de uso parenteral. La obtención de estos anticuerpos naturales anti banda 3 permitirá abordar estudios posteriores acerca de su posible participación y potencial terapéutico en el fenómeno de vasooclusión en la drepanocitosis.

Natural anti-band 3 IgG antibodies were purified by affinity chromatography with an acceptable level of purity, rapidity and efficiency, starting from a mixture of human immunoglobulins of paren teral use. The attainment of these natural anti-band 3 antibodies will allow further studies on their possible participation and therapuetic potential in the phenomenon of drepanocytosis vasoocclusion.

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Band 3 (AE1) is one of the most abundant proteins in the membrane of the human erythrocyte. This protein works as an anionic CI - and HCO3- exchanger and it also functions as an anchor for several proteins of the erythrocyte's cytoesqueleton. Several mutations have been described and many polymorphic variants have been associated to hereditary spherocytosis. The identification of a genetic marker at position 5' of the AEl gene could be associated to several molecular defects of the erythrocyte. This genetic marker is a restriction fragment length polymorphism (RFLP) produced by restriction enzime Pst I. For this polymorphism a total of 216 individuals belonging to seven different populations were analyzed: one from the Central Valley, two African descendants (Lim6n and Guanacaste) and four Amerindians (Bribri, Cabecar, Maleku and Guaymi). The most frequent allele in the Amerindian population was no 1. No significant differences were found with respect to the Hardy-Weinberg equilibrium in six of the populations, although the Guaymi group does present significative differences.

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