Naturally occurring anti-band 3 antibodies

Erythroid disturbances before and after treatment of Portuguese psoriasis vulgaris patients: a cross-sectional and longitudinal study

BACKGROUND

A few studies in psoriasis vulgaris patients have reported changes suggesting red blood cell (RBC) damage is linked to neutrophil activation, oxidative stress, and psoriasis worsening.

OBJECTIVE

The aim of this study was to evaluate erythroid disturbances in Portuguese psoriasis vulgaris patients, before, during, and after treatment.

METHODS

A cross-sectional study (n = 73 patients vs 40 healthy control subjects) followed by a longitudinal study (n = 47 patients) was performed, with assessments before, and at 3, 6, and 12 weeks of therapy (10 patients started topical treatment, 17 narrow-band UVB, and 20 photochemotherapy [psoralen plus UVA; PUVA]). Evaluations included hematologic data, total bilirubin levels, membrane-bound hemoglobin (MBH), membrane protein band 3 profile, total plasma antioxidant status (TAS), lipid peroxidation (thiobarbituric acid [TBA] assay), elastase, lactoferrin, and C-reactive protein (CRP).

RESULTS

Before treatment, patients presented with higher leukocyte/neutrophil and reticulocyte counts, elastase, lactoferrin, TBA, TBA/TAS, reticulocyte production index, total bilirubin and MBH values, lower RBC and hematocrit, higher percentages of high-molecular-weight aggregates, and lower percentages of band 3 monomer. After treatment, we observed a reversal in most of the parameters. However, patients still presented with values suggestive of accelerated RBC damage, removal, and production, as most of the parameters were still higher than those in the control group; the same occurred with CRP.

CONCLUSION

Our data suggest that psoriasis vulgaris triggers an inflammatory response, with release of acute-phase reactants, reactive oxygen species, cationic proteins, and proteases, leading to enhanced RBC damage/aging and, ultimately, to enhanced RBC removal. These assumptions were strengthened by the observation that, with treatment, all of these changes were reversed, the inflammation was reduced, the production of reticulocytes was increased, and the RBCs presented changes usually observed in younger/less damaged RBCs. These erythroid changes were enhanced with PUVA therapy, probably due to the more pronounced clearing of the lesions, as suggested by Psoriasis Area and Severity Index (PASI) scores. Finally, after treatment, a residual inflammation still persisted that might contribute to the observed erythroid disturbances.

Peroxiredoxin-2 as a candidate biomarker to test oxidative stress levels of stored red blood cells under blood bank conditions

BACKGROUND

Several researches on aging red blood cells (RBCs)--performed both in vivo and under blood bank conditions--revealed that RBC membrane proteins undergo a number of irreversible alterations, mainly due to oxidative stress. The individuation of proteins to be used as indicators of irreversible RBC injury and to be proposed as candidate biomarkers of oxidative damage or aging status during blood storage is therefore of great interest.

STUDY DESIGN AND METHODS

Based on this purpose we performed proteomic analysis of the membranes of RBCs during various storage periods under blood bank conditions. Changes in protein composition of RBC membranes were monitored as a function of the storage period by means of polyacrylamide gel electrophoresis coupled with immunoblotting and mass spectrometry analyses.

RESULTS

During storage, a progressive linkage of typical cytosolic proteins to the membrane was detected, including both antioxidant and metabolic enzymes (such as catalase, peroxiredoxin-2 [Prx2], and 2,3-bisphosphoglycerate-mutase), as well as nonreducible cross-linkings of probably oxidized or denatured hemoglobin. This phenomenon was unequivocally related to oxidative stress, since storage of RBCs under anaerobic conditions showed a suppression of these protein recruitments to the membrane.

CONCLUSION

The detailed analysis of these protein associations to the membrane of aged RBCs allowed Prx2 to be suggested as a potential RBC oxidative stress marker for the sake of developing new approaches in quality assurance of blood components.

Erythrocyte changes in preeclampsia: relationship between maternal and cord blood erythrocyte damage

Our aim was to evaluate red blood cell (RBC) changes in normal and preeclamptic cases, and to assess the relationship between maternal and umbilical cord blood (UCB) changes. We evaluated markers of RBC damage: membrane bound hemoglobin (MBH) and band 3 profile - high molecular weight aggregates (HMWSAg), monomer and proteolytic fragments. RBCs are marked for removal by a rise in MBH and in HMWAg. Preeclamptic mothers had significantly higher MBH, RBC count, hemoglobin, hematocrit, reticulocytes and reticulocyte production index (RPI). In UCB from newborns of preeclamptic mothers, we found similar HMWAg, RBC count, hemoglobin and hematocrit; significantly higher MBH, mean cell hemoglobin concentration, mean cell volume, RPI and reticulocyte count. Maternal MBH and HMWAg values were positively and significantly correlated with MBH and HMWAg values in UCB, in normal as well as in preeclamptic pregnancies; in preeclampsia, a significant positive correlation between UCB and maternal bilirubin, and between RPI and proteinuria were found. We conclude that markers of RBC damage/production are altered in preeclampsia, in both UCB and maternal circulation. Our data show similarities between UCB and maternal RBC changes, as suggested by the correlations of markers of RBC damage.

Enhanced suicidal death of erythrocytes from gene-targeted mice lacking the Cl-/HCO(3)(-) exchanger AE1

Genetic defects of anion exchanger 1 (AE1) may lead to spherocytic erythrocyte morphology, severe hemolytic anemia, and/or cation leak. In normal erythrocytes, osmotic shock, Cl(-) removal, and energy depletion activate Ca(2+)-permeable cation channels with Ca(2+)-induced suicidal erythrocyte death, i.e., surface exposure of phosphatidylserine, cell shrinkage, and membrane blebbing, all features typical for apoptosis of nucleated cells. The present experiments explored whether AE1 deficiency favors suicidal erythrocyte death. Peripheral blood erythrocyte numbers were significantly smaller in gene-targeted mice lacking AE1 (AE1(-/-) mice) than in their wild-type littermates (AE1(+/+) mice) despite increased percentages of reticulocytes (AE1(-/-): 49%, AE1(+/+): 2%), an indicator of enhanced erythropoiesis. Annexin binding, reflecting phosphatidylserine exposure, was significantly larger in AE1(-/-)erythrocytes/reticulocytes ( approximately 10%) than in AE1(+/+) erythrocytes ( approximately 1%). Osmotic shock (addition of 400 mM sucrose), Cl(-) removal (replacement with gluconate), or energy depletion (removal of glucose) led to significantly stronger annexin binding in AE1(-/-) erythrocytes/reticulocytes than in AE1(+/+) erythrocytes. The increase of annexin binding following exposure to the Ca(2+) ionophore ionomycin (1 muM) was, however, similar in AE1(-/-) and in AE1(+/+) erythrocytes. Fluo3 fluorescence revealed markedly increased cytosolic Ca(2+) permeability in AE1(-/-) erythrocytes/reticulocytes. Clearance of carboxyfluorescein diacetate succinimidyl ester-labeled erythrocytes/reticulocytes from circulating blood was more rapid in AE1(-/-) mice than in AE1(+/+) mice and was accelerated by ionomycin treatment in both genotypes. In conclusion, lack of AE1 is associated with enhanced Ca(2+) entry and subsequent scrambling of cell membrane phospholipids.

Erythropoietin levels in the different clinical forms of hereditary spherocytosis

Erythropoietin (EPO), the main growth factor responsible for the regulation of red blood cell production, may be overproduced when blood loss or haemolysis occurs. Patients with mild hereditary spherocytosis (HS) are able to maintain normal haemoglobin concentration, whereas typical and severe HS patients develop an anaemic state. Splenectomy usually reverses anaemia. We aimed to clarify the role of EPO in the response to enhanced spherocyte destruction, and to look for a linkage with the broad clinical spectra of HS. EPO levels, reticulocyte count and production index (RPI), other parameters used to classify HS and the protein deficiencies underlying HS were evaluated in previously diagnosed unsplenectomised (n = 24) and splenectomised (n = 10) patients presenting mild, typical or severe HS. A significant increase in EPO was observed in all unsplenectomised HS patients. In the mild form, a significant correlation of EPO with reticulocyte count and RPI was observed; however, this correlation disappeared in typical HS patients. Splenectomised HS patients presented a correction in EPO levels in all forms of HS, although the reticulocyte count and RPI sustained slightly higher values. Our data show HS as a disease linked to an overproduction of EPO, according to the severity of the disease; however, a disturbance in erythropoiesis seems to occur in typical HS. Moreover, splenectomy leads to a correction in the EPO levels.

Band 3 as a marker of erythrocyte changes in pregnancy

Modifications in the erythrocyte membrane protein band 3 seem to mark the cell for death. A decrease in band 3 high molecular weight aggregates (HMWAg) and a rise in its proteolytic fragments (Pfrag) were described for younger erythrocytes. The aim of this work was to study the band 3 profile as a marker of erythrocyte changes in pregnancy and postpartum. We performed a cross-sectional study in non-pregnant controls (n = 24), in women in the first (n = 64), second (n = 48) and third (n = 67) trimesters of gestation, and also in the puerperium (24-48 h after delivery; n = 32); we also carried out a longitudinal study (n = 23) during the three trimesters of normal pregnancy. We evaluated the band 3 profile (% of band 3 monomer, HMWAg, and Pfrag) and the membrane-bound haemoglobin. Total serum bilirrubin, glutathione peroxidase activity, red blood cell (RBC) count, haematocrit (Ht), haemoglobin (Hb) concentration, the haematimetric indices, and red cell distribution width were also evaluated. Similar results were found in pregnancy in both the cross-sectional and longitudinal studies. We found that the RBC count, Hb, and Ht decreased significantly in pregnancy and in puerperium. Band 3 profile in the first trimester of pregnancy, when compared with controls, presented significantly reduced HMWAg and increased Pfrag. Comparing the first with the third trimester, we found a significant reduction in band 3 and a significant rise in Pfrag. However, between these same periods, HMWAg did not decrease. Our data suggest band 3 profile as a marker of erythrocyte changes in pregnancy, which are independent of the 'physiological anaemia' of pregnancy. These changes suggest an increase in damaged RBCs, but also an increase in younger RBCs in the maternal circulation.

Influence of oxidation and crosslinking on oxygen binding properties of mouse erythrocytes

Different chemical treatments for mouse erythrocyte modification has been used. Oxidation treatments with Ascorbate/Fe(3+), a system able to react with intracellular proteins, produced a displacement of the O(2) binding equilibrium curve to a higher affinity behaviour with loss of the haemoglobin cooperativity for oxygen binding. Incubation of mouse erythrocytes with diamide showed that at low reagent concentration (0.8 mM) no modification on oxygen binding equilibrium curves was observed. At higher reagent concentration (2.0 mM), an increased affinity and a disappearance of the cooperative behaviour can be observed. Additionally, crosslinking reactions on mouse erythrocytes with band 3 crosslinkers seemed to affect oxygen binding properties when used at a crosslinker concentration of 5 mM. Oxyhaemoglobin levels in crosslinked and diamide-treated erythrocytes are similar to those found in control cells. In contrast, ascorbate/Fe(3+) treatments produced an increment in the proportion of methaemoglobin, decreasing the oxyhaemoglobin levels in these oxidized erythrocytes.

Leukocyte activation, erythrocyte damage, lipid profile and oxidative stress imposed by high competition physical exercise in adolescents

BACKGROUND

The aim of this study was to evaluate and to compare the lipid profile and the levels of leukocyte activation, red blood cell (RBC) damage and of oxidative stress in two groups of adolescents, with similar body mass index: high competition swimmers and adolescents practising moderate regular physical exercise.

METHODS

As markers of leukocyte activation, we measured plasma lactoferrin, elastase and granulocyte-monocyte colony stimulating factor. We studied RBC membrane band 3 profile and membrane-bound hemoglobin, as markers of RBC damage and aging; total and differential leukocyte count and RBC count, hematocrit, hemoglobin concentration and hematimetric indexes were also measured. Lipid profile included the evaluation of triglycerides (TG), total cholesterol (Chol), high-density lipoprotein cholesterol (HDLc), low-density lipoprotein cholesterol (LDLc), apolipoproteins AI and B (Apo AI and B), and lipoprotein (a) (Lp(a)). To evaluate oxidative stress, lipoperoxidation products and total antioxidant capacity were measured.

RESULTS

We found that high competition adolescents presented increased plasma levels of leukocyte activation products, increased RBC damage suggesting aging and premature removal, and higher oxidative stress. Lipid profile showed some risk and some protective changes.

CONCLUSIONS

Our data suggest that high competition exercise, by imposing a higher and sustained oxidative and proteolytic stress, may contribute in the future to a higher risk of cardiovascular disease. We believe these findings warrant a reevaluation of current views in the intensity, duration and regularity of physical exercise, and that the evaluation of leukocyte activation products, RBC damage, oxidative stress and lipid profile may represent good markers to establish putative protective thresholds.

Erythrocyte membrane band 3 profile imposed by cellular aging, by activated neutrophils and by neutrophilic elastase

The aim of this study was to evaluate in vitro the modifications in the profile of erythrocyte membrane protein band 3 (monomer, aggregates and fragments) imposed by cellular aging, by activated neutrophils (AN) and by neutrophilic elastase. The modifications imposed by cellular aging were evaluated in fractions of less dense and dense red blood cells (RBCs). To evaluate the changes imposed by AN, suspensions of RBCs and AN were used, in a ratio similar to or higher than that described elsewhere for individuals post-myocardial infarction (Santos-Silva A et al. Atherosclerosis 1995; 116:199-209). Neutrophilic elastase was used at increased concentrations. We found that the modifications imposed upon band 3 profile by AN and neutrophilic elastase were significantly correlated with AN and elastase concentration, and were similar to those presented by cellular aging. We propose band 3 profile as a useful cumulative marker of oxidative and/or proteolytic stress conditions, namely those arising from normal RBC aging or from an accelerated aging process imposed by stressful situations, such as inflammatory diseases.

The anti-erythrocyte autoimmune response of NZB mice. Identification of two distinct autoantigens

With age, New Zealand black (NZB) mice spontaneously develop anti-mouse red blood cell (RBC) autoantibodies resulting in the development of autoimmune haemolytic anemia (AIHA). Previously, we characterized a panel of monoclonal autoantibodies derived from unimmunized, adult NZB mice. One of these antibodies (G8) was shown to be pathogenic, inducing AIHA in a non-autoimmune-prone mouse strain (BALB/c). Using G8, and two other antibodies from our panel, we have characterized two distinct autoantigens on the surface of mouse RBCs. The autoantigen, historically referred to as antigen X (AgX), was found to be partially hidden on the surface of the mouse RBC because glycosidase treatment or mild digestion with proteinase K resulted in increased reactivity with autoantibodies. One of the monoclonal antibodies (3H5G1) was found to immunoprecipitate a 110,000 MW protein identified as the erythrocyte anion transporter (band 3) whereas the pathogenic antibody (G8) as well as a third monoclonal antibody (2E6m) were shown to immunoprecipitate a 60,000 MW protein that was not reactive with the anti-band 3 serum. Finally, we show that the autoantigen recognized by G8 is expressed on differentiated mouse erythroleukaemia (MEL) cells. The results suggest that a protein distinct from band 3 can serve as a target for AIHA in NZB mice.

Targeting of mouse erythrocytes by band 3 crosslinkers

Chemical conditions of crosslinking mouse erythrocytes with BS3 and DTSSP have been studied. These two crosslinking reagents seem to react with band 3 protein in mouse erythrocytes membrane. Extent of crosslinking is dependent on the concentration of the reagent used. Similar cell volumes were observed in crosslinked erythrocytes with respect to control erythrocytes. In vivo behaviour of these modified erythrocytes revealed prominent targeting of crosslinked erythrocytes to liver. This effect is clearly evident when concentrations of 5 mM BS3 or DTSSP were used and can be dependent of reagent concentration. Consequently, from our results BS3 and DTSSP can be considered as very useful tools to control and modulate targeting of crosslinked erythrocytes.

Origin of blood-group antigens: a self-declaration mechanism in somatic cell society

Blood-group antigens have been developed as a self-declaration mechanism in higher organisms, since blood cells carry different DNA from that of germ-line cells, and their selfishness must be strictly limited. If not, symbiosis between somatic DNA and germ-line DNA cannot be maintained since blood cells can express autonomy programmed within themselves. For the sake of maintenance of symbiosis, this self-declaration is not limited to blood cells and all somatic cells need a self-plural declaration mechanism such as blood-group antigens. Differentiation and development including induction and inhibition also depend on the self-declaration--recognition mechanism.

Altered erythrocyte membrane band 3 profile as a marker in patients at risk for cardiovascular disease

The aim of this study is to evaluate the correlation between a rise in blood neutrophil concentration and cellular and molecular changes of erythrocytes, among populations presenting an increased risk of cardiovascular disease (CVD). A population of men aged 20-65 years was used which included 22 post-myocardial infarction individuals (< 48 h), 24 survivors of myocardial infarction (> 3 months), 12 hypertensive individuals and 29 individuals presenting normal haematological values and normal lipid profile. The lipid profile parameters used to ascertain increased risk of CVD included triglycerides (TG), total cholesterol (Chol), high-density lipoprotein cholesterol (HDLc), low-density lipoproteins cholesterol (LDLc) and apolipoproteins A1 (Apo A1) and B (Apo B). The hematological parameters measured were concentration of total white blood cells (WBC) and of the several leukocyte types; concentration of red blood cells (RBC); hematocrit (Ht); hemoglobin concentration (Hb); mean cell volume (MCV); activity of erythrocyte glucose-6-phosphate dehydrogenase (G6PD); band 3, its aggregates and fragments in erythrocyte membranes, the percentage of membrane-bound hemoglobin (MBH), and the linkage of immunoglobulin G (IgG) to erythrocyte membrane. We found that the MBH and the band 3 profile is different in control as compared to pathological groups and that, as expected, the aggregation of band 3 promotes the linkage of IgG to the erythrocyte membrane. A negative correlation was shown between total neutrophils and both total RBCs and erythrocyte G6PD activity. We suggest that the erythrocyte, a cell that undergoes and accumulates oxidative and proteolytic damage along its life span, may provide a useful model of oxidative and proteolytic stress in CVD and that band 3 may represent a useful marker of that stress.

An indirect effect of an antibody on complement deposition and lysis of differently sensitized surrounding cells

Lysis of papain-treated group A and B erythrocytes by human complement was studied by an anti-A (BRIC. 131) and an anti-B (BRIC. 30) IgM monoclonal antibody in 51Cr release assays. The indirect effect of membrane-bound antibody, i.e. its influence on complement binding to sensitized surrounding cells, was examined in a cold target competition test in which sensitized, non-labelled cells are present along with sensitized labelled cells and complement. The mode by which anti-A antibodies indirectly suppressed lysis of sensitized B cells up to 20-fold was studied by following C1q and C3b binding. C1q binding to both types of erythrocytes was not altered in mixed populations of erythrocytes in the presence of both antibodies. Binding of C3b to a mixture of both cell types was, however, suppressed, when both antibodies were present. C3b deposition in mixed cell populations did not reach a significantly higher extent than deposited to one type of erythrocyte alone. This was consistent with the results from competitive lysis and suggests that the anti-A captured most C3b at high anti-A concentrations and deprived the similarly sensitized B erythrocytes of complement. We think that this phenomenon is not due to an uneven removal of complement regulatory proteins from A and B erythrocytes by papain. Instead, the phenomenon might be due to an inherent property of anti-A mAb to better produce nucleation sites for C3 convertases which, upon binding factor B, better compete for the limiting factor D. A mathematical analysis of cold target competition experiment (containing 2430 individual measurements) also shows that the distribution of complement between the competing A and B erythrocyte population is uneven, since it predicts that in any given antibody combination the majority of complement is bound to A erythrocytes. This is consistent with the measured average percentage of lysis.

Band 3 protein: structure, flexibility and function

The electroneutral exchange of chloride and bicarbonate across the human erythrocyte membrane is facilitated by Band 3, a 911 amino acid glycoprotein. The 43 kDa amino-terminal cytosolic domain binds the cytoskeleton, haemoglobin and glycolytic enzymes. The 52 kDa carboxyl-terminal membrane domain mediates anion transport. The protein is a functional dimer, in which the two subunits probably interact with one another by an allosteric mechanism. It is proposed that the link between the mobile cytoplasmic and the membrane-spanning domains of the protein is flexible, based on recent biochemical, biophysical and structural data. This explains the long-standing puzzle that attachment to the cytoskeletal spectrin and actin does not appear to restrict the rotational movement of the Band 3 protein in the erythrocyte membrane. In the Band 3 isoform from the Southeast Asian Ovalocytes (SAO) this link is altered, resulting a tighter attachment of the cytoskeleton to the plasma membrane and a more rigid red blood cell.