Human platelets express gangliosides with LKE activity and ABH blood group activity

ABO Incompatibility between the Mother and Fetus Does Not Protect against Anti-Human Platelet Antigen-1a Immunization by Pregnancy

(1) Background: ABO blood group incompatibility between the mother and fetus protects against anti-D immunization by pregnancy. The possible role of ABO incompatibility in protecting against anti-human platelet antigen-1a immunization is unclear. (2) Methods: This study retrospectively screened 817 families (mother-father-neonate trios) of suspected fetal and neonatal alloimmune thrombocytopenia for inclusion. ABO genotypes were determined in 118 mother-child pairs with confirmed alloimmune thrombocytopenia due to anti-HPA-1a antibodies, and 522 mother-child pairs served as the control group. The expression of blood group antigen A on platelets was determined in 199 consecutive newborns by flow cytometry and compared with adult controls. (3) Results: ABO incompatibility between mother and fetus did not protect against anti-human platelet antigen-1a immunization by pregnancy. ABO blood groups of mothers and/or fetuses were not associated with the severity of fetal and neonatal alloimmune thrombocytopenia. The expression pattern of blood group A antigens on the platelets of newborns mirrored that of adults, albeit on a lower level. Blood group A antigen was detected on a subpopulation of neonatal platelets, and some newborns revealed high platelet expression of A determinants on all platelets (type II high-expressers). (4) Conclusion: The lack of a protective effect of ABO incompatibility between mother and fetus against anti-human platelet antigen-1a immunization by pregnancy may indicate that fetal platelets are not the cellular source by which the mother is immunized.

Function of Platelet Glycosphingolipid Microdomains/Lipid Rafts

Lipid rafts are dynamic assemblies of glycosphingolipids, sphingomyelin, cholesterol, and specific proteins which are stabilized into platforms involved in the regulation of vital cellular processes. The rafts at the cell surface play important functions in signal transduction. Recent reports have demonstrated that lipid rafts are spatially and compositionally heterogeneous in the single-cell membrane. In this review, we summarize our recent data on living platelets using two specific probes of raft components: lysenin as a probe of sphingomyelin-rich rafts and BCθ as a probe of cholesterol-rich rafts. Sphingomyelin-rich rafts that are spatially and functionally distinct from the cholesterol-rich rafts were found at spreading platelets. Fibrin is translocated to sphingomyelin-rich rafts and platelet sphingomyelin-rich rafts act as platforms where extracellular fibrin and intracellular actomyosin join to promote clot retraction. On the other hand, the collagen receptor glycoprotein VI is known to be translocated to cholesterol-rich rafts during platelet adhesion to collagen. Furthermore, the functional roles of platelet glycosphingolipids and platelet raft-binding proteins including G protein-coupled receptors, stomatin, prohibitin, flotillin, and HflK/C-domain protein family, tetraspanin family, and calcium channels are discussed.

ABO Blood Group as a Model for Platelet Glycan Modification in Arterial Thrombosis

ABO blood groups have long been associated with cardiovascular disease, thrombosis, and acute coronary syndromes. Many studies over the years have shown type O blood group to be associated with lower risk of cardiovascular disease than non-type O blood groups. However, the mechanisms underlying this association remain unclear. Although ABO blood group is associated with variations in concentrations of circulating von Willebrand Factor and other endothelial cell adhesion molecules, ABO antigens are also present on several platelet surface glycoproteins and glycosphingolipids. As we highlight in this platelet-centric review, these glycomic modifications may affect platelet function in arterial thrombosis. More broadly, improving our understanding of the role of platelet glycan modifications in acute coronary syndromes may inform future diagnostics and therapeutics for cardiovascular diseases.

Markers for characterization of bone marrow multipotential stromal cells

Given the observed efficacy of culture-expanded multipotential stromal cells, also termed mesenchymal stem cells (MSCs), in the treatment of graft-versus host and cardiac disease, it remains surprising that purity and potency characterization of manufactured cell batches remains rather basic. In this paper, we will initially discuss surface and molecular markers that were proposed to serve as the indicators of the MSC potency, in terms of their proliferative potential or the ability to differentiate into desired lineages. The second part of this paper will be dedicated to a critical discussion of surface markers of uncultured (i.e., native) bone marrow (BM) MSCs. Although no formal consensus has yet been reached on which markers may be best suited for prospective BM MSC isolation, markers that cross-react with MSCs of animal models (such as CD271 and W8-B2/MSCA-1) may have the strongest translational value. Whereas small animal models are needed to discover the in vivo function on these markers, large animal models are required for safety and efficacy testing of isolated MSCs, particularly in the field of bone and cartilage tissue engineering.

Impact of ABO incompatibility on engraftment and transfusion requirement after unrelated cord blood transplantation: a single institute experience in Japan

The impact of ABO incompatibility between donor and recipient on engraftment and transfusion requirement was studied in 95 adults who underwent unrelated cord blood transplantation (CBT). The patients included 27 ABO-identical, 29 minor, 21 major and 18 bidirectional ABO-incompatible recipients. Neutrophil engraftment did not differ between ABO-identical/minor ABO-incompatible and major/bidirectional ABO-incompatible recipients (hazard ratio (HR) 1.17, P=0.48). Cumulative incidence of platelet engraftment in ABO-identical/minor ABO-incompatible recipients was higher than in major/bidirectional ABO-incompatible recipients (HR 1.88, P=0.013). In addition, fewer platelet transfusions were required during the first 60 days after CBT in ABO-identical/minor ABO-incompatible recipients (HR 0.80, P=0.040). RBC engraftment did not differ between the two groups (HR 1.25, P=0.33). However, fewer RBC transfusions were required in ABO-identical/minor ABO-incompatible recipients than in major/bidirectional ABO-incompatible recipients (HR 0.74, P<0.005). No patients developed pure red-cell aplasia after CBT. These results indicate that ABO incompatibility affected platelet engraftment and transfusion requirement of RBC and platelet in CBT recipients. Further studies including larger patient numbers are required to elucidate the impact of ABO incompatibility on the clinical outcome of CBT.

Monoclonal antibody B2, a marker of neuroendocrine sympathoadrenal precursors, recognizes the Luke (LKE) antigen

BACKGROUND

Blood group antigens are physiologically important differentiation markers in embryogenesis and development. Monoclonal antibody (MoAb) B2 recognizes a transient antigen expressed on late sympathoadrenal neuroendocrine precursors and early sympathetic neuroblasts. It has been suggested that MoAb B2 may recognize a globo-series glycosphingolipid (GSL) related to the P blood group family.

STUDY DESIGN AND METHODS

MoAb B2 and two anti-LKE MoAbs, MC813-70 and RM1, were screened against a panel of GSL standards and isolated red blood cell (RBC) GSLs by high-performance thin layer chromatography (HPTLC) immunostaining. The ability of all three MoAbs to bind intact RBCs and two LKE+ renal cell carcinoma cell lines (A498, ACHN) were examined by flow cytometry and hemagglutination.

RESULTS

MoAbs B2, MC813-70, and RM1 all specifically recognized monosialogalactosylgloboside (MSGG) on HPTLC immunostaining. Only MoAb MC813-70 bound intact RBC by flow cytometry and hemagglutination. Differential staining was observed between the three antibodies and two renal cell carcinoma cell lines.

CONCLUSION

MoAb B2 recognizes MSGG or LKE antigen, suggesting that LKE may play a role in neuroendocrine differentiation from neural crest cells. Although MoAb B2 is not suitable for RBC phenotyping, it may be a useful immunologic reagent for the identification of human embryonic stem cells and renal cell and embryonic carcinoma.

Determinants of ABH expression on human blood platelets

Platelets express ABH antigens, which can adversely effect platelet transfusion recovery and survival in ABH-incompatible recipients. To date, there has been no large, comprehensive study comparing specific donor factors with ABH expression on platelet membranes and glycoconjugates. We studied ABH expression in 166 group A apheresis platelet donors by flow cytometry, Western blotting, and thin layer chromatography relative to donor age, sex, A1/A2 subgroup, and Lewis phenotype. Overall, A antigen on platelet membranes, glycoproteins, and glycosphingolipids was linked to an A1 red blood cell (RBC) phenotype. Among A1 donors, platelet ABH varied significantly between donors (0%-87%). Intradonor variability, however, was minimal, suggesting that platelet ABH expression is a stable, donor-specific characteristic, with 5% of A1 donors typing as either ABH high- or low-expressers. Group A2 donors, in contrast, possessed a Bombay-like phenotype, lacking both A and H antigens. Unlike RBCs, ABH expression on platelets may be determined primarily by H-glycosyltransferase (FUT1) activity. Identification of A2 and A1 low expressers may increase the availability and selection of crossmatched and HLA-matched platelets. Platelets from group A2 may also be a superior product for patients undergoing A/O major mismatch allogeneic progenitor cell transplantation.

Inverse expression of P(k) and Luke blood group antigens on human RBCs

BACKGROUND

Luke (LKE) is a high-frequency RBC antigen, related to the P blood group system. A LKE-negative phenotype is found in 1 to 2 percent of donors and may be associated with increased P(k). Because P(k) and similar glycolipids are receptors for shiga toxin on cell membranes, a LKE-negative phenotype could have implications for infections by Shigella dysenteriae and enterohemorrhagic Escherichia coli.

STUDY DESIGN AND METHODS

Volunteer donors (n = 257) were serologically typed for LKE with a LKE MoAb, MC813-70. LKE-strong-positive, LKE-weak-positive and LKE-negative RBCs were analyzed for P(k), P, LKE, and shiga toxin binding by immunofluorescence flow cytometry, high-performance thin-layer chromatography, scanning densitometry, and high-performance thin-layer chromatography immunostaining.

RESULTS

Among Iowa donors, 78.6 percent were LKE-strong-positive, 20.2 percent were LKE-weak-positive, and 1.2 percent were LKE-negative. There was an inverse expression of P(k) and LKE on RBCs. P(k) expression was increased on LKE-negative RBCs and was associated with increased shiga toxin binding. A LKE-active glycolipid was identified in the ganglioside fraction of LKE-strong-positive RBCs.

CONCLUSION

A LKE-negative phenotype is associated with increased expression of P(k) on RBCs. Differences in P(k) and LKE expression may play a role in host susceptibility to infection with S. dysenteriae and E. coli.