Overview of the diversity of erythrocyte blood group antigens

During the differentiation and maturation of erythrocytes, the surface molecules of erythrocytes are gradually expressed and stabilized. These molecules are to be antigenic in addition to their functions of maintaining cell membrane structural stability, material transport and exchange of cells and signal transmission between cells. The antigenic molecules on the erythrocyte surface are called erythrocyte blood group antigens. The blood group antigens and their corresponding blood group antibodies in vivo are important indicators for clinical blood transfusion and organ transplantation, and also form the basis for research on blood group related diseases. Three hundred and sixty-eight erythrocyte blood group antigens have been confirmed so far, which are classified into 39 blood group systems, 5 blood group collections and 2 blood group series. Based on the diversity of blood group antigens and their composition of glycolipids, glycoproteins and other molecules, this study mainly reviews the classification, molecular structure, antibody response and gene regulation of blood group antigens, and explains the main reasons for the diversity of blood group antigens.     

Surface receptors on lymphoreticular cells: sensory devices for host recognition of foreign antigens and neoplasia.

Distinct types of cells in the lymphoreticular system regulate an individual''s immunologic homeostasis and response to disease. By means of multiple receptors the cell membrane transfers signals between the environment and the cell. This article reviews the important surface antigens and receptors on normal and activated macrophages (e.g., receptors for the crystallizable fragment [Fc] of immunoglobulin), on lymphocytes derived from the bone marrow (e.g., immunoglobulins and immune-associated [Ia] antigens), on thymus-derived lymphocytes (e.g., Thy-1 antigens) and on "null'' cells. Although many of these markers were originally defined in rodents and birds, analogous markers in humans have proved extremely useful in characterizing lymphoreticular cell populations in healthy and sick individuals. Established and postulated functions of the markers in host defence mechanisms are discussed.     

Reactive oxygen species: the unavoidable environmental insult?

Reactive oxygen species (ROS) are generated by a variety of sources from the environment (e.g., photo-oxidations and emissions) and normal cellular functions (e.g., mitochondrial metabolism and neutrophil activation). ROS include free radicals (e.g., superoxide and hydroxyl radicals), nonradical oxygen species (e.g., hydrogen peroxide and peroxynitrite) and reactive lipids and carbohydrates (e. g., ketoaldehydes, hydroxynonenal). Oxidative damage to DNA can occur by many routes including the oxidative modification of the nucleotide bases, sugars, or by forming crosslinks. Such modifications can lead to mutations, pathologies, cellular aging and death. Oxidation of proteins appears to play a causative role in many chronic diseases of aging including cataractogenesis, rheumatoid arthritis, and various neurodegenerative diseases including Alzheimer's Disease (AD). Our goal is to elucidate the mechanism(s) by which oxidative modification results in the disease. These studies have shown that (a) cells from old individuals are more susceptible to oxidative damage than cells from young donors; (b) oxidative protein modification is not random; (c) some of the damage can be prevented by antioxidants, but there is an age-dependent difference; and (d) an age-related impairment of recognition and destruction of modified proteins exists. It is believed that mechanistic insight into oxidative damage will allow prevention or intervention such that these insults are not inevitable. Our studies are also designed to identify the proteins which are most susceptible to ROS damage and to use these as potential biomarkers for the early diagnosis of diseases such as AD. For example, separation of proteins from cells or tissues on one- and two-dimensional gels followed by staining for both total protein and specifically oxidized residues (e.g., nitrotyrosine) may allow identification of biomarkers for AD.     

Biochemistry of the erythrocyte Rh polypeptides: a review

The clinically important Rh blood group system is complex, consisting of multiple distinct antigens. Despite clinical recognition for over 50 years, the Rh blood group antigens have remained poorly understood on a molecular level until the recent identification and characterization of the "Rh polypeptides," the core structural proteins of the Rh antigens. This group of erythrocyte membrane proteins of molecular weight 30,000-35,000 daltons was first recognized by employing Rh-specific antibodies to immunoprecipitate radiolabeled components of erythrocyte membranes. By using antibodies specific for the Rh D, c, and E antigens, a series of highly related non-identical proteins were immunoprecipitated, indicating that the Rh antigens are composed of multiple related proteins. The Rh polypeptides have been purified and characterized, and they were found to have several unusual biochemical characteristics. The Rh polypeptides penetrate the membrane bilayer; they are linked to the underlying membrane skeleton; they are covalently fatty acid acylated with palmitate. While the Rh antigenic reactivity is unique to human erythrocytes, the Rh polypeptides have been isolated from erythrocytes of diverse species and are thought to be fundamental components of all mammalian erythrocyte membranes. The functional role of the Rh polypeptides remains undefined, but a role in the organization of membrane phospholipid is suspected.     

Vesicle-mediated transport of membrane and proteins in malaria-infected erythrocytes

Malaria parasites during intraerythrocytic development change the ultrastructure, biophysics, and the antigens of the host red blood cell membrane. Parasite-encoded proteins are associated with, inserted into, or secreted across the infected erythrocyte membrane. Since parasites of the genus Plasmodium are eukaryotic cells, it must be assumed that they possess essentially eukaryotic modes of vesicle-mediated transport and translocation of proteins and membranes. Numerous studies have demonstrated vesicular structures in the cytoplasm of malaria-infected red blood cells and an assortment of parasite proteins associated with the different vesicles, membranes, and membrane-defined compartments. Some parasite polypeptides remain trapped between the parasite and the parasitophorous vacuole membranes PVM, whereas others are associated with morphologically distinct membrane-limited vesicles and vacuoles. Some of these same parasite protein antigens also associate with the erythrocyte membrane or with parasite-induced ultrastructural modifications in the membrane of the parasitized red blood cells. This implies that intracellular transport occurs in malaria-infected erythrocytes, a capacity that uninfected red blood cells normally lose upon enucleation. The specific locations of parasite antigens within the infected cell also implys the existence of targeting signals in the translocated parasite polypeptides and perhaps transport-mediating proteins. The genes corresponding to some of these translocated proteins have been sequenced. Typical (and in some cases atypical) signal peptide sequences occur, as well as a number of sequences that may result in posttranslational modifications. How or if these features figure in to the translocation across, and targeting to a particular membrane compartment of the intraerythrocytic parasite remains unknown.(ABSTRACT TRUNCATED AT 250 WORDS)     

Structural relationships between human erythrocyte sialoglycoproteins beta and gamma and abnormal sialoglycoproteins found in certain rare human erythrocyte variants lacking the Gerbich blood-group antigen(s).

The human erythrocyte membrane sialoglycoproteins beta and gamma are important for the maintenance of the discoid shape of the normal erythrocyte. In this paper we show that the human erythrocyte sialoglycoproteins beta and gamma (hereafter called beta and gamma) are structurally related. Rabbit antisera produced against purified beta and beta 1 and rendered specific to the cytoplasmic portion of these proteins also react with the cytoplasmic portion of gamma. Some human anti-Gerbich (Ge) sera react with the extracellular portion of both beta and gamma. This reactivity is shown to be directed towards a common epitope on beta and gamma. However, most anti-Ge sera do not react with beta, but react with an extracellular epitope only present on gamma. All individuals who lack the Ge antigens lack beta and gamma. In some cases abnormal sialoglycoproteins are present in the erythrocytes, and these are shown to be structurally related to beta and gamma. Rabbit antisera raised against the purified abnormal sialoglycoprotein from a Ge-negative erythrocyte type reacted with the cytoplasmic portion of both beta and gamma. Unlike normal beta and gamma, the abnormal sialoglycoproteins found in Ge-negative erythrocytes migrate as a diffuse band on SDS/polyacrylamide-gel electrophoresis. Studies using endoglycosidases suggest that the diffuse nature of these bands results from carbohydrate heterogeneity and that the abnormal sialoglycoproteins contain N-glycosidically linked oligosaccharides with repeating lactosamine units. Such polylactosamine chains are not present on normal beta or gamma.     

Topology of bovine red cell antigens as a function of the organization of their genes

Bovine erythrocytes from genetically defined animals were examined by electron microscopy for cell surface distribution of their antigens as a function of the organization of genes coding for the antigens. No blocking or inhibition of labeling was found when cells were double-labeled for two antigens whose genes resided in a) cis or trans conformations within the same blood group system (R₂ and W antigens of the C system), or b) in different blood group systems (R₂ and Z antigens of theC and Z systems, respectively). The results suggest that these antigens are probably distinct moieties on the cell surface rather than a series of determinants on a common backbone macromolecule. Genes coding for these antigens are, therefore, probably arranged in the genome as separate but closely linked genes and not as a series of multiple alleles, each allele coding for several serological determinants. A nonreciprocal increase in labeled sites was found on labeling two particular antigens within the same blood group system (R₂ and X₂ antigens of the C system). By absorption a parallel serological effect was also found for this pair of antigens.     

Polyamines--sickling red blood cell interaction.

The binding of polyamine as a function of concentration to normal and sickling rcc'. blood cells is analyzed by Langmuir type binding isotherms, based on the Gouy-Chapman model for an electrical double Iayer, where the zeta potential is a function of only the normal distance coordinate. For normal erythrocytes, the apparent exotropic binding constants are found to be 103, 110, and 130 dl/g at normal distance coordinates of 4, 5, and 6 Å, iezpectively. The esotropic binding constant is determined to be 420 dl/g at a distance of 7 Å. For sickling red blood cells, the apparent exotropic binding constants are 3.3, 3.8, 4.6, and 6-7 dl/g at a distance of 4 to 7 Å. The esotropic binding constant at a distance of 8 Å is found to be 12-9 dl/g. The apparent binding affinity of polyamines to the normal red blood cell. therefore, is approximately 30 times greater than to the sickling erythrocyte.The Praxis pulse nuclear magnetic resonance spectrometer is used to determine the spin-lattice relaxation time (T₁) for water in the presence of normal and sickling red blood cells. The spin-lattice relaxation time is found to be 540 ms for normal erythrocytes and 445 ms for sickling red blood cells in the oxy state. Differences in the spin-spin relaxation time (T₂) for the two types of erythrocyte are negligible, being within the range of normal experimental error.     

Alloantigens common to erythrocytes and leucocytes in pigs

The presence of pig blood group antigens Ea, Ed, Ef, El and Gb has been demonstrated on pig lymphocytes by the cytotoxic test. The typing of standard blood group reagents in an erythrocyte panel and cytotoxic antisera in a lymphocyte panel (from the same individuals as the erythrocytes) showed that the reactions of some sera with cytotoxic activity corresponded to the distribution of the given erythrocyte antigens.     

Proteomic study of a model causative agent of harmful algal blooms, Prorocentrum triestinum II: the use of differentially expressed protein profiles under different growth phases and growth conditions for bloom prediction

Simultaneous comparison of differentially expressed protein profiles of Prorocentrum triestinum grown under different growth phases and growth conditions indicated the presence of phase-specific and stress-responsive proteins, respectively. Correlation studies on these proteins in relation to cell division phasing patterns and to models of phytoplankton growth inferred the possible functions. Most notable among these proteins were groups of proteins thought to trigger or mediate cells through specific phases of division of this alga, e.g., BP1, BP2, PB1, PB2, and PB3. Other proteins (e.g., group 1 proteins) thought to be responsible for maintaining and supporting cell concentration under adverse conditions were found. Furthermore, another group of proteins (group 2 proteins) thought to be stress-responsive were also detected. Taken overall, these differentially expressed proteins provided important information for uncovering various protective and adaptive mechanisms in the dinoflagellate's life cycle. These proteins have the potential to serve as "indicator proteins" for rapid assessment of the nutritional or metabolic status of these phytoplankton cells,and monitoring the differential expression of these phase-specific proteins and stress-specific proteins could be an important biomarker for bloom prediction.     

Trafficking of malarial proteins to the host cell cytoplasm and erythrocyte surface membrane involves multiple pathways

During the asexual stage of malaria infection, the intracellular parasite exports membranes into the erythrocyte cytoplasm and lipids and proteins to the host cell membrane, essentially "transforming" the erythrocyte. To investigate lipid and protein trafficking pathways within Plasmodium falciparum-infected erythrocytes, synchronous cultures are temporally analyzed by confocal fluorescence imaging microscopy for the production, location and morphology of exported membranes (vesicles) and parasite proteins. Highly mobile vesicles are observed as early as 4 h postinvasion in the erythrocyte cytoplasm of infected erythrocytes incubated in vitro with C6-NBD-labeled phospholipids. These vesicles are most prevalent in the trophozoite stage. An immunofluorescence technique is developed to simultaneously determine the morphology and distribution of the fluorescent membranes and a number of parasite proteins within a single parasitized erythrocyte. Parasite proteins are visualized with FITC- or Texas red-labeled monoclonal antibodies. Double-label immunofluorescence reveals that of the five parasite antigens examined, only one was predominantly associated with membranes in the erythrocyte cytoplasm. Two other parasite antigens localized only in part to these vesicles, with the majority of the exported antigens present in lipid-free aggregates in the host cell cytoplasm. Another parasite antigen transported into the erythrocyte cytoplasm is localized exclusively in lipid-free aggregates. A parasite plasma membrane (PPM) and/or parasitophorous vacuolar membrane (PVM) antigen which is not exported always colocalizes with fluorescent lipids in the PPM/PVM. Visualization of two parasite proteins simultaneously using FITC- and Texas red-labeled 2 degrees antibodies reveals that some parasite proteins are constitutively transported in the same vesicles, whereas other are segregated before export. Of the four exported antigens, only one appears to cross the barriers of the PPM and PVM through membrane-mediated events, whereas the others are exported across the PPM/PVM to the host cell cytoplasm and surface membrane through lipid (vesicle)-independent pathways.     

Immunological biochips for studies of human erythrocytes

Immunological microarrays (biochips) for detecting erythrocyte surface antigens, viz., blood group antigens (A, B, 0) and Rhesus system antigens (D, E, e, C, and c), are described. The biochips represent transparent plastic supports onto which 1.5-mm spots of specific immobilized antibodies (IgM) are coated in different dilutions. The volume of tested blood samples is rather small (1–2 μl). Binding of erythrocytes to antibodies immobilized on the biochips is specific and allows further morphological analysis of bound cells. Analysis of the dynamics of cell detachment from biochip spots using a microfluidic chamber at different flow rates of the washing solution showed that combination of a biochip with a microfluidic chamber is a promising approach to concentration of cells of various immunotypes even if their content in the mixture is very low.     

The role of mast cell-derived secreted phospholipases A2 in respiratory allergy

Secreted phospholipases A₂ (sPLA₂s) are molecules released in plasma and biological fluids of patients with systemic inflammatory, autoimmune and allergic diseases. These molecules exert proinflammatory effects by either enzymatic-mechanisms or through binding to surface molecules expressed on inflammatory cells. sPLA₂s are released at low levels in the normal airways and tend to increase during respiratory allergies (e.g., rhinitis and bronchial asthma) as the result of local secretion. Several sPLA₂ isoforms are expressed in the human lung and some of them (e.g., group IIA and group X) are released in the airways of patients with rhinitis or asthma. Mast cells play a major role in the pathogenesis of respiratory allergies and other chronic inflammatory lung diseases. Recent evidence indicates that mast cells purified from human lung express most of the sPLA₂ isoforms so far described. IgE-mediated activation of these cells induce the release of sPLA₂s suggesting that mast cells are a main source of extracellular sPLA₂s during allergic reactions. Once released, sPLA₂s may contribute to the generation of eicosanoids (e.g., PGD₂ and LTC₄) and to the release of preformed mediators (e.g., histamine) by an autocrine loop involving the interaction of sPLA₂s with surface molecules such as heparan sulphate proteoglycans or the M-type receptor. Thus, mast cell-derived sPLA₂s may play an important role in the initiation and amplification of the inflammatory reactions in patients with allergic rhinitis and bronchial asthma.     

Separation of human erythrocyte membrane associated proteins with one-dimensional and two-dimensional gel electrophoresis followed by identification with matrix-assisted laser desorption/ionization-time of flight mass spectrometry

A classical proteomic analysis was used to establish a reference map of proteins associated with healthy human erythrocyte ghosts. Following osmotic lysis and differential centrifugation, ghost proteins were separated by either one-dimensional gel electrophoresis (1-DE) or two-dimensional gel electrophoresis (2-DE). Selected protein bands or spots were excised and trypsinized before mass spectrometric analyses and data mining was performed using the SWISS-PROT and NCBI nonredundant databases. A total of 102 protein spots from a 2-D gel were successfully identified. These corresponded to 59 distinct polypeptides with the remaining 43 being isoforms. As for the 1-D gel, 44 polypeptides were identified, of which 19 were also found on the 2-D gel. Most of the 19 common polypeptides were membrane cytoskeletal proteins that are often referred to as the "band" proteins. The remaining 25 polypeptides that were found exclusively on 1-D gels were proteins with high hydrophobicity (e.g., sorbitol dehydrogenase and glucose transporter) and high molecular mass (e.g., Kell blood group glycoprotein and Janus-kinase 2). A higher number of signaling proteins was also identified on 1-D gels compared to 2-D gels. These included Ras, cAMP dependent protein kinase and TGF-beta receptor type 1 precursor.     

The distribution of type-2 chain histo-blood group antigens in normal cycling human endometrium

Summary The blood group ABO(H) determinants are major allogenic antigens in both erythrocytes and tissue of man. These antigens and related carbohydrates are markers of cellular maturation and differentiation in many epithelial tissues and have recently attracted great interest as tumor-associated antigens. Previous studies of endometrial tissues have indicated that glycosylation in this tissue may be related to hormonal stimulation. We have investigated the immunohistochemical distribution of type-2 chain histo-blood group-related carbohydrates in specimens of normal, cycling endometria obtained from hysterectomies on women with known ABO/Lewis erythrocyte type and saliva secretor status. N-acetyllactosamine and Le^x were demonstrated to be uninfluenced by the genetic background. A and Ale^y antigens were exclusively demonstrated in endometria from blood group A individuals, while Le^y was expressed in endometria from blood group 0 individuals mainly. The precursor N-acetyllactosamine as well as the terminal H, A, and ALe^y antigens were shown in only a few cells. In contrast, N-acetyllactosamine substituted by sialic acid and/or fucose residues (Le^x, sialosyl-Le^x, Le^y) were demonstrated in epithelial cells of normal, cycling endometrium, but with both quantitative and qualitative differences in staining relating to the menstrual cycle, indicating that type-2 chain antigens are expressed under both genetic and hormonal influence in human cycling endometrium.     

Feature selection environment for genomic applications

Background  

Feature selection is a pattern recognition approach to choose important variables according to some criteria in order to distinguish or explain certain phenomena (i.e., for dimensionality reduction). There are many genomic and proteomic applications that rely on feature selection to answer questions such as selecting signature genes which are informative about some biological state, e.g., normal tissues and several types of cancer; or inferring a prediction network among elements such as genes, proteins and external stimuli. In these applications, a recurrent problem is the lack of samples to perform an adequate estimate of the joint probabilities between element states. A myriad of feature selection algorithms and criterion functions have been proposed, although it is difficult to point the best solution for each application.     

Nodamura virus nonstructural protein B2 can enhance viral RNA accumulation in both mammalian and insect cells

During infection of both vertebrate and invertebrate cell lines, the alphanodavirus Nodamura virus (NoV) expresses two nonstructural proteins of different lengths from the B2 open reading frame. The functions of these proteins have yet to be determined, but B2 of the related Flock House virus suppresses RNA interference both in Drosophila cells and in transgenic plants. To examine whether the NoV B2 proteins had similar functions, we compared the replication of wild-type NoV RNA with that of mutants unable to make the B2 proteins. We observed a defect in the accumulation of mutant viral RNA that varied in extent from negligible in some cell lines (e.g., baby hamster kidney cells) to severe in others (e.g., human HeLa and Drosophila DL-1 cells). These results are consistent with the notion that the NoV B2 proteins act to circumvent an innate antiviral response such as RNA interference that differs in efficacy among different host cells.     

Association of ABO blood group and outcome of coccidioidal infection

Dissemination of fungal infection due to Coccidioides immitis has been previously shown to be related to hereditary factors. Two associations reported to date are race (e.g., Filipino and black ancestry) and HLA histocompatibility type (HLA-19). In the present study of 105 patients a significant association of blood group B and dissemination is demonstrated. C. immitis is known to possess antigens with blood group A activity. Previous epidemiologic studies have also shown HLA-A9 and blood group B are both more common in persons of black and Filipino ancestry. Further studies are needed to define whether these are independent variables, and may define subgroups at particularly high risk following coccidioidal infection.     

Molecular and cellular biology of malaria

Thanks to the extensive use of recombinant DNA technology and immunological methods, much insight into cellular functions of the human malaria parasite Plasmodium falciparum has been gained since it was learnt ten years ago how to grow this organism in culture. The amino acid sequence of over a dozen surface proteins of the parasite and of several proteins the parasite excretes into its most important host cell, the erythrocyte, have been determined. Interestingly many of these proteins show blocks of repeated amino acids. Several proteins have been shown to be involved in specific aspects of the complex hostparasite interaction, such as penetration of host cells or increased stickiness of infected red blood cells in the blood vessels. Some of the proteins described here may be protective antigens and may become important in vaccine development.     

The basics of thiols and cysteines in redox biology and chemistry

Cysteine is one of the least abundant amino acids, yet it is frequently found as a highly conserved residue within functional (regulatory, catalytic, or binding) sites in proteins. It is the unique chemistry of the thiol or thiolate group of cysteine that imparts to functional sites their specialized properties (e.g., nucleophilicity, high-affinity metal binding, and/or ability to form disulfide bonds). Highlighted in this review are some of the basic biophysical and biochemical properties of cysteine groups and the equations that apply to them, particularly with respect to pK_a and redox potential. Also summarized are the types of low-molecular-weight thiols present in high concentrations in most cells, as well as the ways in which modifications of cysteinyl residues can impart or regulate molecular functions important to cellular processes, including signal transduction.