In addition, patients may be transfused with blood components such as red blood cells, platelets or fresh frozen plasma, which may be required to support them while they are receiving chemotherapy to treat a cancer or because they have an illness that prevents production of adequate numbers of these blood components. Experienced nursing staff monitor all treatments. A variety of apheresis procedures are performed in our dedicated apheresis unit. We collaborate with the MGH Bone Marrow Transplant BMT Service to collect hematopoeitic stem cells from patients and normal donors for autologous and allogeneic stem cell transplants respectively.
We collaborate with the MGH research community to collect T cells from patients for a variety of research protocols. We provide clinical consultation for therapeutic plasmapheresis to treat a variety of autoimmune and hematologic conditions including, but not limited to, Guillain-Barre syndrome, ANCA-positive vasculitides, anti-GBM disease, hyperviscosity syndrome, and thrombotic thrombocytopenic purpura.
Physicians interested in these services can contact our Blood Bank resident by calling and paging number Illustration of blood group systems. Shown here are general schematics of the structures of major blood group systems that include carbohydrates, single-pass transmembrane proteins, multipass transmembrane proteins, and glycosylphosphatidylinositol-linked proteins. Types of DNA sequence variation.
Top SNVs result from the substitution of one base, whereas insertion or deletion indel affects a string of nucleotides. Reprinted with permission from Johnsen et al. The ABO gene seems deceptively simple, spanning only 7 exons, and the majority of known ABO genetic variants are also seemingly relatively simple, primarily comprising SNVs and a handful of small indels. However, ABO serologic discrepancies, when they occur, require additional testing. Additionally, in some clinical scenarios platelet transfusion, transplant , knowledge of ABO subtype can guide clinical decision making.
Thus, in genetically assigning ABO, all 3 genes are considered.
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The most common cause of D-negative blood type is a whole RHD gene deletion, although other gene disrupting mutations also occur. Conversely, individuals with weak D variants may express D so weakly as to type D negative with clinical antisera but can still express enough D to be both tolerant to D as recipients and capable of provoking an anti-D alloimmune response in a D-negative recipient. Together, ABO and RH are examples of blood group systems that exhibit the spectrum of genetic and functional variation observed across all blood group systems.
ABO harbors relatively simple genetic variation but has hundreds of alleles and a gene that indirectly generates blood group antigens. Conversely, the RH locus directly encodes the proteins presenting DCE antigens, but it is multigenic; the Rh proteins are complex multipass transmembrane domains, and their genes exhibit both simple and complex structural variation. Allosensitization is the direct result of exposure to allogenic blood type mismatch es and can lead to significant morbidity and mortality from acute HTRs, delayed HTRs DHTRs , and hemolytic disease of the fetus and newborn, which affects up to 1 in pregnancies.
The risk of DHTRs is even more common, at 1 per 20, component transfused, 12 with high suspicion that these adverse events are under-recognized and underreported. Matching donor units to patients by blood type, when possible, is the only strategy that can avoid provoking alloimmune reactions attributable to existing alloantibodies and prevent primary allosensitization events.
Extended blood type matching beyond ABO and D has long been proposed as a strategy to reduce alloimmunization.
Now there are many institutions matching for Rh C and E and Kell K antigens, reserving additional blood type match levels for alloimmunized patients. Several of the most common blood group antigens can be rapidly and relatively inexpensively typed this way. However, the identification of unusual variants of the major common antigen systems and typing of minor blood group systems requires the use of reagents often available only in specialized reference laboratories Table 1.
Schematic of blood type testing technologies. Illustrated are the progression of increasing information obtained from different blood type testing technologies: serology left provides data limited to the targets of the antibody, and molecular testing middle provides information on select genetic variants or small genetic regions and can include RFLPs, SSPs, SNPs, and Sanger sequencing.
Purpose of the handbook:
NGS right can capture sequence variation at all blood group gene loci at once. Adapted from Johnsen et al 39 and Singleton et al. Currently, U.
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Large-scale serologic testing of donors is time and resource intensive, and only a small percentage of donors and patients are serologically tested for extended blood types usually E, e, C, c, and K. Individuals harboring other variant blood group antigens are most commonly identified when they allosensitize or during screens of donors for specific antigen-negative units.
In practice, contemporary serologic blood type testing prioritizes prevention of the most common and life-threatening ABO and D transfusion mismatches, followed by a risk-based tiered approach to extended testing.
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When this occurs, allosensitization almost always occurs in one or more blood group antigens not assessed in routine blood type testing. Within the contemporary blood bank laboratory molecular tool kit are variations on older DNA techniques, including single nucleotide polymorphism SNP -specific polymerase chain reaction SSP and restriction fragment length polymorphism RFLP , which are used for investigations of less common blood group variants, especially in Rh. SNPs have been useful in providing unprecedented access to extended blood type profiling at scale, particularly for blood group antigens without available testing reagents.
ABO and RH are not represented on the FDA-approved SNP platform, although other molecular tools providing genetic information in these systems are available commercially, as laboratory developed tests, and several are in development. With advancements in technologies to enable testing genetic variants at scale, particularly for SNPs, the practice of using genetically informed blood group antigens has begun to be adopted more widely in blood centers and transfusion services.
The main detractors to saturation of genotyping for blood typing have been cost and turnaround time relative to serology. Both of these have decreased markedly in recent years, and, when compared with extended serologic typing or alloantibody identification workups, genetic testing compares favorably. In blood donors, the scale of genotyping can be used to optimize and manage deep inventories of multiple antigen-negative units, and it has even been proposed that blood group genotypes may be useful as a donor recruiting tool.
There is concern that current SNP strategies exhibit ethnic bias. In a recent study of blood type frequencies in Asian and Native Americans, an SNP-based strategy for blood typing was studied and found to have generally high concordance with the 5 blood group antigens tested by serology C, Jk a , Jk b , M, and N. DNA sequencing remains the only approach that can capture relatively unbiased genetic variation by virtue of the ability to detect genetic variation whether it is known, rare, or novel.huangkhalapplanen.ga
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Sanger sequencing remains a well-established method for identifying blood type genetic variants for particularly difficult cases in the transfusion reference laboratory. With advances in next-generation sequencing NGS technology, DNA sequencing can now be performed at the scales needed for more comprehensive and high-resolution blood type genotyping.
The success of NGS is demonstrated by the large number of publications in recent years, and NGS is now implemented for numerous clinical applications, including pharmacogenomics, inherited congenital syndromes, inherited cancer risk genes, and tumor profiling. NGS can provide high-resolution blood group DNA sequence information that is too cumbersome to obtain by Sanger sequencing and cannot be ascertained by other lower-resolution molecular methods Figure 3.
Adjustments to sequencing protocols, such as seeking increased read depth or longer DNA sequence reads, can facilitate detection of CNVs and more complex variants. Statistical and machine learning approaches are now being applied successfully to identify variants and accurately and reproducibly call genotypes. However, other NGS technologies are at various stages of development for review, see Johnsen et al 39 , which may in the future prove to be useful for blood group gene DNA sequencing, particularly the long-read DNA sequencing technologies.
Recent proof-of-concept NGS efforts are now demonstrating the feasibility of sequencing all blood group genes in a targeted capture DNA sequencing approach the general method for targeted sequencing is illustrated in Figure 4 , as well as WGS.
Molecular Protocols in Transfusion Medicine : Gregory A Denomme :
Schematic of one form of targeted NGS. Adapted with permission from Johnsen et al. Blood group gene variants were further annotated as to being previously reported or associated with named blood type alleles and cross-referenced with the donor's corresponding serologic blood type for ABO, D, C, Jk a , Jk b , M, and N and SNP data 24 SNPs to call 38 blood group antigens. Calls of RHD blood group antigens used a combination of SNV and small indel calls, as well as analysis for whole gene RHD deletion events determined by normalized read depth.
Left Whole gene RHD deletions are identified by relative read depth.
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Molecular Protocols in Transfusion Medicine - eBook. Average rating: 0 out of 5 stars, based on 0 reviews Write a review. Tell us if something is incorrect. Book Format: Choose an option. Product Highlights This essential methods manual for immunohematologists or hematologists and immunohematologists provides information on genes that encode antigens on red blood cells, platelets and neutrophils.