Distribution of size and shape in populations of normal human red cells

The diameter, area, and volume of individual human erythrocytes (of 8 subjects, newborn to age 71) were determined by photographing the cells hanging on edge. Measurements from high magnification prints were processed by computer. The distributions of diameter, area, and volume are described statistically, with the unexpectedly linear regression equations for their interrelations. The plot of area vs. volume for the 1016 normal cells from seven subjects (newborn excluded) was remarkably linear with a "straight-line" boundary restricting the distribution. Shape was characterized by a dimensionless "sphericity index" (4.84.volume 2/3 /area). Cells of larger volume tended to be thinner than the smaller cells.

The red cell can easily be deformed at constant volume, but an increase in membrane area results in hemolysis. A theoretical geometric parameter, the "minimum cylindrical diameter" (MCDiam), in microns, the thinnest cylindrical channel through which each individual cell could pass, predicts the linear boundary of the plot of area vs. volume. The MCDiam value of 3.66 µ ± 0.04 SEM accurately represents the thinnest channel through which 95% of the cells can pass.

In two splenectomized patients with hereditary spherocytosis the MCDiam was increased to approximately 4.0 µ, suggesting that the severest restriction is located in the spleen.

Red cell abnormalities in hereditary spherocytosis: relevance to diagnosis and understanding of the variable expression of clinical severity

Marked variations in the clinical manifestations of hereditary spherocytosis (HS) have long been recognized. However, neither the molecular nor the cellular basis for this variable expression has been fully delineated. To better define the cellular basis for variable expression of the disease, we evaluated the pathobiology of red cells in a large series of 55 non-splenectomized and 31 splenectomized patients with HS. Red cell membrane surface area, surface area-to-volume ratio, cell volume, and state of cell hydration were quantitated. We found that decreased membrane surface area was a distinguishing feature of red cells in all patients studied, whereas decreased surface area-to-volume ratio as reflected by increased osmotic fragility was noted in only 66% of the non-splenectomized patients. In terms of red cell indexes, the percentage of microcytes was not a good discriminator of HS phenotype but was the best indicator of the severity of the disease. In contrast, the presence of increased numbers of hyperdense cells was an effective discriminating feature of the HS phenotype but a poor indicator of disease severity. These findings have enabled us to define the dominant cellular changes that account for the variable clinical severity of this common red cell membrane disorder and have allowed development of improved approaches for its diagnosis.

Reductions of erythrocyte membrane viscoelastic coefficients reflect spectrin deficiencies in hereditary spherocytosis

Hereditary spherocytosis is a common hemolytic anemia associated with deficiencies in spectrin, the principal structural protein of the erythrocyte membrane-skeleton. We have examined 20 different individuals from 10 spherocytosis kindreds and 2 elliptocytosis kindreds to determine the effects of different levels of spectrin deficiency on the viscoelastic properties of the erythrocyte membrane. Micropipettes were used to perform single-cell micromechanical measurements of approximately 1,000 individual cells to determine the membrane elastic shear modulus, the apparent membrane bending stiffness, and whole cell recovery time constant for the different cell populations. The membrane viscosity was calculated by the product of the shear modulus and the recovery time constant. Results show correlation between the fractional reduction in shear modulus and the fractional reduction in spectrin content (determined by spectrin radioimmunoassay) and spectrin density (determined by the ratios of spectrin to band 3 on electrophoresis gels) suggesting that membrane shear elasticity is directly proportional to the surface density of spectrin on the membrane (P less than 0.001). The apparent membrane bending stiffness is also reduced in proportion to the density of spectrin (P less than 0.001). The membrane viscosity is reduced relative to control (P less than 0.001), but the nature of the relationship between spectrin density and membrane viscosity is less clearly defined. These studies document striking relationships between partial deficiencies of erythrocyte spectrin and specific viscoelastic properties of the mutant membranes.

Band 3 anion exchanger and its involvement in erythrocyte and kidney disorders

Recent developments in the structure of erythrocyte band 3 and its role in hereditary spherocytosis and distal renal tubular acidosis are described. The crystal structure of the N-terminal cytoplasmic domain provides a basis for understanding the organization of ankyrin and other peripheral membrane proteins around band 3. Band 3 also binds integral membrane proteins, including the Rh protein complex and CD47. Band 4.2 is important in these associations, which link the Rh complex to the skeleton. It is suggested that band 3 forms the scaffold for a protein assembly that could transduce signals from the cell exterior and modulate the transport and mechanical properties of the erythrocyte. The involvement of band 3 in distal renal tubular acidosis is reviewed. The article discusses a likely mechanism for dominant distal renal tubular acidosis in which associations between the normal and mutant protein alter the plasma membrane targeting of the normal protein in the kidney.

Abnormality of CD4(+)CD25(+) regulatory T cells in idiopathic thrombocytopenic purpura

OBJECTIVES

The aim of this study was to explore the profile and function of CD4(+)CD25(+) regulatory T cells (Treg cells) in idiopathic thrombocytopenic purpura (ITP) patients.

METHODS

Treg cell numbers were analyzed by flow cytometric analysis in peripheral blood mononuclear cells collected from healthy donors or patients with ITP. Quantification of cell proliferation was assayed by an enzyme-linked immunosorbent assay kit, based on the measurement of BrdU incorporation during DNA synthesis.

RESULTS

The percentage of Treg cells was significantly decreased in ITP patients in active and non-remission state(5.79 +/- 1.22%) when compared with the patients in remission(11.63 +/- 4.56%) and to healthy subjects(12.68 +/- 3.59%). The suppressive activity of Treg cells in ITP patients was also found to be impaired.

CONCLUSION

These results suggest that decreased number and function of Treg cells might be one of mechanisms that cause immune regulation dysfunction in ITP.

Mechanics of diseased red blood cells in human spleen and consequences for hereditary blood disorders

In red blood cell (RBC) diseases, the spleen contributes to anemia by clearing the damaged RBCs, but its unique ability to mechanically challenge RBCs also poses the risk of inducing other pathogenic effects. We have analyzed RBCs in hereditary spherocytosis (HS) and hereditary elliptocytosis (HE), two typical examples of blood disorders that result in membrane protein defects in RBCs. We use a two-component protein-scale RBC model to simulate the traversal of the interendothelial slit (IES) in the human spleen, a stringent biomechanical challenge on healthy and diseased RBCs that cannot be directly observed in vivo. In HS, our results confirm that the RBC loses surface due to weakened cohesion between the lipid bilayer and the cytoskeleton and reveal that surface loss may result from vesiculation of the RBC as it crosses IES. In HE, traversing IES induces sustained elongation of the RBC with impaired elasticity and fragmentation in severe disease. Our simulations thus suggest that in inherited RBC disorders, the spleen not only filters out pathological RBCs but also directly contributes to RBC alterations. These results provide a mechanistic rationale for different clinical outcomes documented following splenectomy in HS patients with spectrin-deficient and ankyrin-deficient RBCs and offer insights into the pathogenic role of human spleen in RBC diseases.

Decreased membrane mechanical stability and in vivo loss of surface area reflect spectrin deficiencies in hereditary spherocytosis

Whereas marked variations in the clinical manifestations of hereditary spherocytosis have long been recognized, we have only recently begun to define the molecular basis for this heterogeneity. An important unanswered question is whether decreased spectrin results in reduced membrane mechanical stability, and if this reduction in membrane mechanical stability can be related to in vivo surface area loss. Using the ektacytometer, we quantitated membrane surface area and stability in erythrocytes from 18 individuals with hereditary spherocytosis and deficiencies of spectrin (30-80% of normal spectrin level). Membrane mechanical stability was reduced and the magnitude of the reductions correlated with the spectrin content. Moreover, the reductions in mechanical stability correlated with in vivo loss of membrane surface area. These data indicate that decreased spectrin content results in reduced membrane mechanical stability and surface area loss in vivo. We conclude that partial deficiencies of spectrin, reductions in membrane mechanical stability, and loss of membrane surface area are directly related and are major features determining the heterogeneous clinical manifestations of hereditary spherocytosis.

Membrane microfilaments of erythrocytes: alteration in intact cells reproduces the hereditary spherocytosis syndrome (vinblastine-colchicine-strychnine-electron microscopy-cell rigidity)

Membrane microfilaments are found throughout the animal world in situations suggesting that they fulfill a critical role in providing normal cell shape and plasticity. We have hypothesized that hereditary spherocytosis, a congenital hemolytic anemia associated with intrinsically rigid and mishapen erythrocytes, might result from genetically defective microfilaments in erythrocyte membranes. By using three different drugs (vinblastine, colchicine, and strychnine) that share one common attribute-that of potently precipitating purified microfilamentous protein-we have provided support for this hypothesis. Thus, all the known in vitro and in vivo characteristics of hereditary spherocytes are reproduced in normal erythrocytes briefly exposed to these precipitating agents.

Experience with eosin-5'-maleimide as a diagnostic tool for red cell membrane cytoskeleton disorders

The diagnosis of hereditary spherocytosis (HS) is based on red cell morphology and other conventional tests such as osmotic fragility, autohemolysis and acidified glycerol lysis. However, milder cases are at times difficult to diagnose. Confirmation by red blood cell (RBC) membrane protein analysis is not possible in most laboratories. Recently, a flow cytometric method has been described for quantitating the fluorescence intensity of intact red cells after incubation with the dye eosin-5'-maleimide (EMA), which binds specifically to the anion transport protein (band-3) at lysine-430. This has been shown to be an effective screening test for red cell membrane disorders. We evaluated the usefulness of this approach for screening membrane protein disorders such as HS and hereditary elliptocytosis (HE) and its value in discriminating this group from other hemolytic anemias, such as glucose-6-phosphate dehydrogenase (G6PD) deficiency, beta-thalassemia trait, sickle cell anemia and autoimmune hemolytic anemia. Fluorescence intensity, expressed in mean channel fluorescence (MCF) units, was determined using a Becton Dickinson FACS Caliber flow cytometer. Membrane protein analysis was carried out by sodium dodecyl sulfate-polyacrylamide gel eletrophoresis (SDS-PAGE). RBCs from patients with HS and HE gave significantly lower MCF values (P < 0.001) than the normal control group and other patient groups. The diagnosis of HS in four cases was confirmed by RBC membrane protein electrophoresis and all showed a deficiency of spectrin. The advantage of the EMA dye method are its specificity for membrane disorders, as well as being a simple, user-friendly and rapid method which is inexpensive, provided a flow cytometer is available.

Abnormal oxidant sensitivity and beta-chain structure of spectrin in hereditary spherocytosis associated with defective spectrin-protein 4.1 binding

Hereditary spherocytosis (HS) is an inherited disorder of erythrocyte shape associated with spectrin deficiency and hemolytic anemia. In a subset of patients with the autosomal dominant form of HS, spectrin displays a reduced capacity to bind protein 4.1 and, therefore, actin; both functions that are critical to the membrane skeleton. A specific structural defect has not been identified in the spectrin from these patients. Chymotryptic digestion of the isolated spectrin chains shows impaired cleavage of the distal peptide of the beta subunit, the beta IV domain. In previous work, we have shown that mild oxidation markedly diminishes the binding capacity of normal spectrin for protein 4.1. Here we observe that chemical reduction of freshly isolated, untreated HS spectrin dramatically improves its function. Thus, a primary structural defect in the beta subunit of spectrin in this subtype of HS may lead to oxidant sensitivity, and secondarily, to a functional defect in the binding of spectrin to protein 4.1 and actin.

Kallmann syndrome in a patient with congenital spherocytosis and an interstitial 8p11.2 deletion

We describe the hitherto smallest interstitial 8p11.2 deletion in a patient with congenital spherocytosis, dysmorphic features, and growth delay in association with hypogonadotropic hypogonadism and anosmia. The latter features are characteristic for Kallmann syndrome. In contrast to the previously reported patients with 8p deletions, the present patient showed normal intelligence. Congenital spherocytosis is one of the most common hereditary hemolytic anemias. One of the three loci for congenital spherocytosis was assigned to chromosome 8p (located between 8p11.1 and 8p21) and mutations in or loss of the ankyrin-1 gene (ANK1) were identified. Molecular analysis confirmed the de novo loss of ANK1 in our patient. Kallmann syndrome, which is characterized by hypogonadotropic hypogonadism and anosmia, can be X-linked, autosomal dominant, or autosomal recessive. So far only the X-linked KAL1 gene has been identified. The present finding suggests an autosomal locus for Kallmann syndrome at 8p11.2. The simultaneous occurrence of congenital spherocytosis, Kallmann syndrome phenotype, dysmorphic features, and growth delay in this patient points to a new contiguous gene syndrome.

Structure of the spleen in idiopathic thrombocytopenic purpura

The structure of the spleens of 12 patients with idiopathic thrombocytopenic purpura (ITP) who underwent splenectomy was studied. The white pulp was characterized by the presence of large numbers of lymphatic nodules containing highly reactive germinal centers. The marginal zone contained large numbers of vessels surrounded by plasma cells. These findings imply active antibody production and are consistent with the concept that the spleen is a major source of antiplatelet antibody production in ITP. Large numbers of platelets in various stages of degradation were seen in cords, particularly in the marginal zone. They appeared both extracellularly and with the cytoplasm of macrophages. It appeared that platelet destruction was initiated by focal cytoplasmic degradation and resulted in formation of cellular debris. These findings indicate that the spleen plays a fundamental role in the pathogenesis of ITP, involving synthesis of antiplatelet antibody, localization of platelets in a milieu rich in this antibody, and subsequently, phagocytosing of immune-damaged platelets.

The human spleen; a histological study in splenectomy specimens embedded in methylmethacrylate

In a series of 316 surgically removed spleens, a histological and supportive immunohistological study was performed on methylmethacrylate sections. The structure of the human white and red pulp differs from the rat spleen in many respects, e.g. the human lacks the marginal sinus and the architecture of the periarteriolar lymph sheath seen in the rat. In man, the lymphoid compartment is in both white and red pulps. In the white pulp separate periarteriolar T-cell areas contain a large lymph-vessel plexus, which was reconstructed in serial sections. The circulation in the red pulp is discussed. The area between the red and white pulp, the perifollicular zone, is not the equivalent of the marginal sinus in the rat. Its anatomy in man suggests that it is an area formed from red pulp during the expansion of new follicles. The micro-anatomy was analysed in 119 controls. In cases of traumatic rupture the white pulp showed evidence of stimulation. A pathognomonic histological picture was not found in idiopathic thrombocytopenic purpura. In haemolytic anaemia the pulp cords were engorged by erythrocytes accompanied by a decreased B/T cell ratio in autoimmune haemolytic anaemia and by an increased B/T cell ratio in congenital spherocytosis.

Near-total splenectomy for hereditary spherocytosis: clinical prospects in relation to disease severity

We prospectively studied the efficacy of near total splenectomy (NTS) for managing hereditary spherocytosis (HS) based on haemoglobin (Hb), total bilirubin and splenic remnant regrowth in 30 children receiving NTS for HS between November 1996 and December 2004 (mean followup 3.6 years). Patients were classified into three severity groups. At followup, mean Hb had increased by 2.9-5.0 g/dl (P = 0.110) and bilirubin dropped by 15.4-56.4 mumol/l. Remnant regrowth was moderate, within the weight-specific norm. Amongst spleen-preserving techniques, NTS shows markedly lower rates of recurrent haemolysis, remnant regrowth and secondary operations, thus potentially benefiting all clinical forms of HS.

Complex Modes of Inheritance in Hereditary Red Blood Cell Disorders: A Case Series Study of 155 Patients

Hereditary erythrocytes disorders include a large group of conditions with heterogeneous molecular bases and phenotypes. We analyzed here a case series of 155 consecutive patients with clinical suspicion of hereditary erythrocyte defects referred to the Medical Genetics Unit from 2018 to 2020. All of the cases followed a diagnostic workflow based on a targeted next-generation sequencing panel of 86 genes causative of hereditary red blood cell defects. We obtained an overall diagnostic yield of 84% of the tested patients. Monogenic inheritance was seen for 69% (107/155), and multi-locus inheritance for 15% (23/155). PIEZO1 and SPTA1 were the most mutated loci. Accordingly, 16/23 patients with multi-locus inheritance showed dual molecular diagnosis of dehydrated hereditary stomatocytosis/xerocytosis and hereditary spherocytosis. These dual inheritance cases were fully characterized and were clinically indistinguishable from patients with hereditary spherocytosis. Additionally, their ektacytometry curves highlighted alterations of dual inheritance patients compared to both dehydrated hereditary stomatocytosis and hereditary spherocytosis. Our findings expand the genotypic spectrum of red blood cell disorders and indicate that multi-locus inheritance should be considered for analysis and counseling of these patients. Of note, the genetic testing was crucial for diagnosis of patients with a complex mode of inheritance.

Inherited hemolytic anemia: a possessive beginner's guide

Significant advances have been made in diagnosis and clinical management of inherited red cell membrane disorders that result in hemolytic anemia. Membrane structural defects lead to hereditary spherocytosis (HS) and hereditary elliptocytosis (HE), whereas altered membrane transport function accounts for hereditary xerocytosis (HX) and hereditary overhydrated stomatocytosis (OHS). The degrees of membrane loss and resultant increases in cell sphericity determine the severity of anemia in HS and HE, and splenectomy leads to amelioration of anemia by increasing the circulatory red cell life span. Alterations in cell volume as a result of disordered membrane cation permeability account for reduced life span red cells in HX and OHS. Importantly, splenectomy is not beneficial in these 2 membrane transport disorders and is not recommended because it is ineffective and may lead to an increased risk of life-threatening thrombosis. Rational approaches are now available for the diagnosis and management of these inherited red cell disorders, and these will be discussed in this review.

Angioid streaks associated with hereditary spherocytosis

We examined members of a family in whom hereditary spherocytosis had appeared in three generations. Angioid streaks were confirmed in the second generation and presumed to exist in the first generation. A woman in the third generation with hereditary spherocytosis did not have angioid streaks but these are age-related and may develop later. The one individual in the second generation without hereditary spherocytosis did not have angioid streaks. Angioid streaks associated with hereditary spherocytosis in this family did not appear to be coincidental. Patients with hereditary spherocytosis should be examined for angioid streaks because of the implications for their vision.

Physiologically important secondary modifications of red cell membrane in hereditary spherocytosis-evidence for in vivo oxidation and lipid rafts protein variations

Hereditary spherocytosis (HS) is a heterogeneous group of disorders. The abnormal red cell morphology (resulting in shortened cell survival) is due to a primary deficiency in spectrin, ankyrin-1, band 3 or protein 4.2. Secondary protein deficiencies are often observed and may be involved in the outcome of the disease. In the present study, we searched for secondary erythrocyte membrane protein alterations in HS, including the lipid raft associated proteins and the oxidative index. For this purpose, 12 patients with clinical and laboratory diagnosis of mild to typical HS were examined. Erythrocyte membrane ghosts and skeletons were subjected to SDS-PAGE and immunoblotting analysis using antibodies against red cell membrane proteins and DNP moiety, after 2,4-dinitrophenylhydrazine derivatization. Protein deficiencies, degradation, aggregation and enhanced binding of cytoplasmic components, band 8, hemoglobin and immunoglobulins G to the membrane as well as increased oxidative index, were found in the majority of the HS patients. Proportion of the membrane- and skeleton-bound globin was oxidized/denatured Hb or hemichromes and crosslinkings. Some HS membranes are deficient in lipid rafts proteins and contain sorcin. A context of these distortions is more pronounced in typical HS cases compared to the mild ones. Similar defects in thalassemia and senescent RBCs are dictated by increased oxidative stress and are positively correlated with perturbations in membrane properties. These data add some new insight in the field of HS pathophysiology and clinical variability.

Hereditary spherocytosis. Recent experience and current concepts of pathophysiology

Hereditary spherocytosis is a clinically heterogeneous, genetically determined red blood cell membrane disorder resulting in hemolytic anemia. A deficiency of spectrin, the largest and most abundant structural protein of the erythrocyte membrane skeleton, results in the formation of spherocytes which lack the strength, durability, and flexibility to withstand the stresses of the circulation. Clinical manifestations of the disease are primarily dependent on the severity of hemolysis, which additionally results in an increased incidence of pigment gallstones. The likelihood of cholelithiasis is directly related to patient age and is uncommon before 10 years of age. Splenectomy is indicated in virtually every patient. When the disease is diagnosed in early childhood, the risk of overwhelming postsplenectomy sepsis makes it advisable to delay splenectomy until after 6 years of age if possible. At the time of splenectomy, it is important to identify and remove any accessory spleens. If gallstones are present, cholecystectomy should be performed. Although spherocytosis persists following splenectomy, hemolysis is alleviated and clinical cure of the anemia is achieved for most patients. Patients with recessively inherited spherocytosis are exceptions. Although they are significantly benefited by splenectomy, their anemia is not completely corrected. Splenectomy reduces hemolysis in all patients and thereby decreases the risk for development of pigment gallstones. Excision of an enlarged spleen removes the danger of traumatic rupture.

The amount of white pulp in the spleen; a morphometrical study done in methacrylate-embedded splenectomy specimens

This report deals with a morphometrical study on 92 surgically removed human spleens, to investigate the composition of spleens which are considered to be normal, i.e. spleens which had ruptured in traffic accidents or which had been incidentally removed during abdominal operations. A comparison was made with 16 spleens with hypersequestration of platelets and to 11 with hyper-sequestration of erythrocytes. Methyl-methacrylate embedding was used because of the superiority of this technique over conventional paraffin embedding. Significant differences were found between both 'normal' groups as to the absolute and relative amount of white pulp as well as the perifollicular red pulp zone. Based also on the few morphometrical reported studies in the literature, spleens removed during abdominal surgery form the best control group. Traumatic rupture of the spleen in traffic accidents might specifically occur in spleens which already contained a stimulated lymphatic compartment. A probably non-specific increase of white pulp was found in splenomegaly of varied aetiology. An expected influence of age on weight and composition of the spleen was not found in our study. The spleen changes in weight and composition only up to 5 years of age. Significant involution at older age was not found in ours nor in other reported larger series.

The human spleen as revealed by scanning electron microscopy

The three-dimensional world of the spleen was explored by scanning electron microscopy on both arterially perfused and nonperfused specimens, as well as on plastic corrosion casts of splenic vasculatures. Of 25 spleens studied, 18 were examples of hypersplenism. These were contrasted to 7 essentially normal spleens taken from children being staged for treatment of Hodgkin's disease whose spleens proved to be uninvolved in the pathologic process. Splenic sinuses in all 25 spleens were typified by a degree of porosity. RBC were caught in the act of entering sinuses from splenic cords. These sinus windows thus represent one end of an "open" circulation pathway. In casts of microvasculature, direct arteriovenous connections were demonstrated, thus establishing an anatomical basis for an often disputed "closed" circulation pathway. Spleens from 7 patients with hereditary spherocytosis had a super abundance of red pulp. Splenic cords were thickened and crowded with spherocytes, many of which presented slightly wrinkled membranes, as were also noted on the peripheral blood RBC. It is possible that these membrane features are unique for HS and reflect the intrinsic membrane abnormality in protein composition. The 7 spleens from chronic idiopathic thrombocytopenic purpura had white pulp as the predominant region. Germinal centers were frequent. Lymphocytes and plasma cells with well-developed microvilli were suggestive that release of antiplatelet antibody might be occurring in white pulp. Platelets were especially notable in peripheral white pulp and marginal zones. Platelet clumps were observed, generally adjacent to spleenic macrophages.