HLA-Mediated Platelet Refractoriness

Immunological platelet transfusion refractoriness: current insights from mechanisms to therapeutics

Although there have been tremendous improvements in the production and storage of platelets, platelet transfusion refractoriness (PTR) remains a serious clinical issue that may lead to various severe adverse events. The burden of supplying platelets is worsened by rising market demand and limited donor pools of compatible platelets. Antibodies against platelet antigens are known to activate platelets through FcγR-dependent or complement-activated channels, thereby rapidly eliminating foreign platelets. Recently, other mechanisms of platelet clearance have been reported. The current treatment strategy for PTR is to select appropriate and compatible platelets; however, this necessitates a sizable donor pool and technical assistance for costly testing. Consolidation of these mechanisms should be of critical significance in providing insight to establish novel therapeutics to target immunological platelet refractoriness. Therefore, the purposes of this review were to explore the modulation of the immune system over the activation and elimination of allogeneic platelets and to summarize the development of alternative approaches for treating and avoiding alloimmunization to human leukocyte antigen or human platelet antigen in PTR.

Platelets retain function and can be stored following disruption of human leucocyte antigens

BACKGROUND AND OBJECTIVES

Antibodies to human leucocyte antigen (HLA) Class-I antigens can lead to refractoriness to platelet transfusion. Although this can be overcome by transfusion of HLA-compatible platelets, they are not always available. Disruption of HLA antigens on platelets by acid treatment may be a suitable alternative when no other components are available. The aim of this study was to assess the effect of HLA disruption and subsequent storage of platelet components.

MATERIALS AND METHODS

Platelet components were treated with 0.9% saline or citric acid solution (pH 3.0), and then stored until expiry (Day 7). HLA and platelet glycoprotein expression, platelet viability, activation and sialylation were measured by flow cytometry. Release of soluble factors was measured by ELISA and metabolism by biochemistry analyser. Reactivity to patient anti-sera containing anti-HLA antibodies was measured using platelet immunofluorescence tests (PIFTs) and monoclonal antibody immobilization of platelet antigen (MAIPA) assays. Platelet function was measured using aggregometry and thromboelastography (TEG).

RESULTS

Acid treatment reduced detection of HLA Class-I on platelets by 75%, with significant reductions in reactivity to patient anti-sera. Acid treatment reduced platelet content and viability, increased platelet activation and accelerated metabolism. Glycan cleavage was increased by acid treatment. Treatment reduced platelet activation following agonist stimulation by ADP and TRAP-6, but platelets remained functional, displaying increased aggregation response and reduced time to clot formation by TEG.

CONCLUSION

Although HLA disruption had some detrimental effects, acid-treated platelets remained functional, retaining their capacity to respond to agonists and form clots, and with further development could be used to support refractory patients.

Investigation of the correlation between platelet antibodies and peripheral blood cytopenia in patients with hepatocellular carcinoma

The primary triggers that stimulate the body to generate platelet antibodies via immune mechanisms encompass events such as pregnancy, transplantation, and blood transfusion. Interestingly, our findings revealed that a subset of male patients with hepatocellular carcinoma (HCC), despite having no history of transplantation or blood transfusion, has shown positive results in platelet antibody screenings. This hints at the possibility that certain factors, potentially related to the tumor itself or its treatment, may affect antibody production. To delve the causes we initiated this study. We employed a case-control study approach to analyze potential influential factors leading to the positive results via univariate and multivariate regression analysis. We utilized Kendall's tau-b correlation to examine the relationship between the strength of platelet antibodies and peripheral blood cytopenia. Antitumor medication emerged as an independent risk factor for positive results in HCC patients, and the strength of platelet antibodies positively correlated with the severity of anemia and thrombocytopenia. Without history of blood transfusion, transplantation, pregnancy, those HCC patients underwent recent tumor medication therapy are experiencing peripheral erythrocytopenia or thrombocytopenia, for them platelet antibody screenings holds potential clinical value for prevention and treatment of complications like drug-immune-related anemia and/or bleeding.

Differentiating patient characteristics between platelet refractory patients with and without antibodies to human leukocyte antigens

BACKGROUND

Predicting whether a patient's platelet refractoriness (PR) is due to immune or nonimmune causes can be challenging. This study compared the demographics and clinical history of PR patients with human leukocyte antigen (HLA) antibodies (HLA-PR) versus PR patients without HLA antibodies.

MATERIALS AND METHODS

A retrospective review of all patients with PR consults at a single institution over a 3-year period was performed. Patient charts were reviewed for all patients with confirmed PR, and demographic information (e.g., sex, race and ethnicity, preferred language) and clinical history (e.g., pregnancy, transfusion, primary diagnosis) were collected. Patient characteristics were compared among the HLA and non-HLA cohorts.

RESULTS

A total of 295 patients with confirmed PR were identified, of whom approximately 70% did not have HLA antibodies and 30% did. Approximately 84% of the HLA-PR cohort was female. A history of transfusions was not associated with HLA-PR (p = .1). A history of pregnancy was strongly associated with the occurrence of HLA-PR (p < .001). Splenomegaly was associated with PR in the absence of HLA alloimmunization whereas infection, fever, bleeding, and disseminated intravascular coagulation were not.

CONCLUSION

In this single-institution retrospective review, a history of pregnancy was strongly associated with HLA-PR, whereas a history of transfusion was not.

Therapeutic plasma exchange in alloimmune platelet refractoriness

Patients with alloimmune platelet refractoriness can present complex clinical conundrums. Herein we describe a case of platelet refractoriness in the setting of combined HLA and HPA alloimmunization in a patient with acute myeloid leukemia and life-threatening bleeding. We discuss causative antibodies and compare prevailing therapeutic modalities. We highlight plasma exchange as a potentially feasible, repeatable, and personalized treatment option for patients with extensive platelet alloimmunization who require transfusion.

Simultaneous genotyping for human platelet antigen systems and HLA-A and HLA-B loci by targeted next-generation sequencing

In order to treat the alloimmunization platelet transfusion refractoriness (PTR), human leukocyte antigen (HLA)-type and/or human platelet antigen (HPA)-type matched platelets between donors and patients are usually used. Therefore, genotyping of HLA-A and HLA-B loci, as well as HPA systems, for donors and patients, is of great significance. However, there is a rare report of genotyping for HLA-A and HLA-B loci as well as HPA systems at the same time. In this study, a high-throughput method for simultaneous genotyping of HLA-A and HLA-B loci, as well as HPA genotyping, was developed. A RNA capture probe panel was designed covering all exon sequences of the GP1BA, GP1BB, ITGA2, CD109, ITGB3, and ITGA2B genes and HLA-A and HLA-B loci. The HLA-A, HLA-B, and 34 HPA systems were genotyped using a targeted next-generation sequencing (NGS) method. The genotypes of the HLA-A and HLA-B loci, as well as the HPA, were assigned based on the nucleotides in the polymorphism sites. Using the NGS method, 204 unrelated blood specimens were successfully genotyped for all 34 HPA systems as well as HLA-A and HLA-B loci. The accuracy of the NGS method was 100%. Only HPA-2, HPA-3, HPA-5, HPA-6w, HPA-15, and HPA-21w showed polymorphism with frequencies of 0.9412, 0.6863, 0.9853, 0.9779, 0.4314, and 0.9951 for a allele, respectively. Thirty-two single nucleotide variants (SNVs) were detected. Of them, 12 SNVs can lead to amino acid change. HLA-A*11:01 and HLA-B*46:01 are the most common alleles for HLA-A and HLA-B loci. A targeted next-generation sequencing method for simultaneously genotyping HPA systems and HLA-A and HLA-B loci was first established, which could be used to create a database of HLA-typed and/or HPA-typed unrelated donors.

Current Status of and Global Trends in Platelet Transfusion Refractoriness From 2004 to 2021: A Bibliometric Analysis

Platelet transfusion refractoriness (PTR) is common in patients with hematology and oncology and is becoming an important barrier in the treatment of thrombocytopenia and hemorrhage. Bibliometrics is an effective method for identifying existing research achievements, important breakthroughs, current research hotspots, and future development trends in any given field. In recent years, research on PTR has received increasing attention, but a bibliometric analysis of this field has not yet been reported. In this study, we applied bibliometrics to analyze the existing literature on PTR research over the past 17 years. On November 1, 2021, we began a publications analysis of PTR research using the Science Citation Index Expanded of the Web of Science Core Collection with collection dates from 2004 to 2021. This research aimed to summarize the state of PTR research using Bibliometrix to identify connections between different elements (i.e., authors, institutions, countries, journals, references, and keywords) using VOS viewer analyses to visualize key topics and trends in PTR research using Cite Space and gCLUTO. The results of all 310 studies showed that the annual number of publications focused on PTR is steadily increasing, with the United States of America and Japan making significant contributions. We noted that the research group led by Dr. Sherrill J. Slichter was prominent in this field, while Estcourt Lise may become the most influential newcomer. Transfusion was the most popular journal, and Blood was the most cited journal. Using various analyses, including co-cited analysis, historiography analysis, citation burst analysis, and factorial analysis, we pointed out and discussed contributing publications. According to occurrence analysis, co-word biclustering analysis, landform map, thematic evolution, and thematic map, we believe that “activation,” “p-selection,” “CD36 deficiency,” “gene-frequencies,” “CD109,” “HPA-1,” and “beta (3) integrin” may become new trends in PTR research. The outcome of our bibliometric analyses has, for the first time, revealed profound insights into the current state and trends in PTR research. The systematic analysis provided by our study clearly demonstrates the field's significant advancements to all researchers who are interested in a quick and comprehensive introduction to the field.

Generation of HLA Universal Megakaryocytes and Platelets by Genetic Engineering

Patelet transfusion refractoriness remains a relevant hurdle in the treatment of severe alloimmunized thrombocytopenic patients. Antibodies specific for the human leukocyte antigens (HLA) class I are considered the major immunological cause for PLT transfusion refractoriness. Due to the insufficient availability of HLA-matched PLTs, the development of new technologies is highly desirable to provide an adequate management of thrombocytopenia in immunized patients. Blood pharming is a promising strategy not only to generate an alternative to donor blood products, but it may offer the possibility to optimize the therapeutic effect of the produced blood cells by genetic modification. Recently, enormous technical advances in the field of in vitro production of megakaryocytes (MKs) and PLTs have been achieved by combining progresses made at different levels including identification of suitable cell sources, cell pharming technologies, bioreactors and application of genetic engineering tools. In particular, use of RNA interference, TALEN and CRISPR/Cas9 nucleases or nickases has allowed for the generation of HLA universal PLTs with the potential to survive under refractoriness conditions. Genetically engineered HLA-silenced MKs and PLTs were shown to be functional and to have the capability to survive cell- and antibody-mediated cytotoxicity using in vitro and in vivo models. This review is focused on the methods to generate in vitro genetically engineered MKs and PLTs with the capacity to evade allogeneic immune responses.

Transfusion Blood Bank (Recipient) Testing

Pretransfusion and post-transfusion recipient testing are routine blood bank functions. This article presents a review of request and sample requirements, routine and extended typing and antibody evaluation, and post-transfusion circumstances requiring additional work-up. Although the regimented approach of blood banking fundamentals may be viewed as tedious, these steps are defined and designed to prevent potentially fatal ABO-incompatible transfusions and improve the overall safety of transfusion medicine patients.

Ex Vivo Manufacture of Megakaryocytes and Platelets from Stem Cells: Recent Advances Toward Transfusion in Humans

The generation of ex vivo functional megakaryocytes (MK) and platelets is an important issue in transfusion medicine as donor dependence implies in limitations, such as shortage of eligible volunteers. Indeed, platelet transfusion is still a procedure that saves the lives of patients with defective platelet production. Recent technological development has enabled the isolation and expansion of stem cells that can be used as a source for the production of functional platelets for transfusion. In this review, we discuss recent approaches of in vitro or ex vivo production of MK and platelets, suggesting that, in the near future, donor-independent sources may become a possibility. The feasibility of using these cells in the clinic may be safer, and in vitro manipulation could generate universally compatible products, solving problems related to platelet refractoriness. However, functionality and survival testing of these products in human beings are scarce; therefore, additional studies are needed to consolidate this purpose.

Platelet transfusion refractoriness and anti-HLA immunization

Platelet transfusion refractoriness (PTR), defined as an unsatisfactory post-transfusion platelet count increment, is a common complication of patients receiving multiple transfusions. Different strategies are described in the management of PTR. In this work, we demonstrate the efficacy of the detection and identification of anti-HLA antibodies in the recipient using a threshold of 3000 mean fluorescence intensity (MFI), and the seek of donors not expressing HLA antigens against which the patient is immunized.

Platelet Refractoriness: Examining Associated Morbidity and Mortality

Platelet refractoriness is defined as the failure of platelets to show adequate increment after platelet transfusion. Platelets are important to the normal clotting and hemostasis process in the prevention of bleeding. Platelet refractoriness is a significant clinical concern because of resulting hemorrhagic emergencies, increased length of hospital stays, higher inpatient costs, and decreased survival. As part of the healthcare team, oncology nurses play a crucial role in early detection and using evidence-based management strategies for platelet refractoriness to limit the potential for associated morbidity and mortality.

Platelet transfusion refractoriness: how do I diagnose and manage?

Platelet refractoriness continues to be a problem for thrombocytopenic patients because the risk of a major spontaneous or life-threatening bleed significantly increases when platelet counts drop below 10 × 109/L. The majority of patients have nonimmune causes driving the refractoriness, such as bleeding, medications, or diffuse intravascular coagulation; however, this article is dedicated to the diagnosis and support of patients with immune-based platelet refractoriness. Antibodies to class I HLA molecules (A and B alleles) are responsible for most immune-based refractory cases, with antibodies to platelet antigens seen much less frequently. Patients may be supported with either crossmatch-compatible or HLA-matched/compatible platelet units. When trying to select HLA units it can be difficult to find a perfect "4 of 4" match for the patient's class IA and IB alleles. In these cases, it is better to use the antibody specificity prediction method, which identifies compatible units that lack antigens recognized by the patient's anti-HLA antibodies. For an algorithmic approach to the patient with platelet refractoriness, see Visual Abstract.

Human Leukocyte Antigen Alloimmunization and Alloimmune Platelet Refractoriness

Despite significant advancements in the production of platelet products, storage, and transfusion, transfusion refractoriness remains a significant clinical problem, affecting up to 14% of hematological patients receiving platelet transfusions. Human leukocyte antigen (HLA) alloimmunization is a major cause of immune platelet refractoriness, and its rate can be significantly reduced by implementation of leukoreduction. Despite promising preclinical results, pathogen reduction does not reduce HLA alloimmunization. Patients with HLA alloimmune refractoriness are usually managed with HLA-selected platelet transfusions. In this review, we describe the pathophysiology of HLA alloimmunization and alloimmune refractoriness, as well as options to prevent and treat these transfusion complications. We discuss the evidence supporting these options and point out the outstanding gaps. Finally, we review the possible future directions for prevention and treatment of alloimmune refractoriness.

Clinical and immunological features of platelet transfusion refractoriness in young patients with de novo acute myeloid leukemia

Platelet transfusion is important in the prevention and treatment of bleeding in patients with acute myeloid leukemia (AML) after receiving intensive chemotherapy. However, platelet transfusion refractoriness (PTR) is an intractable clinical issue occurred in these patients. And its clinical and immunological features remain largely unknown. The potential causes and clinical features of PTR were retrospectively analyzed in 560 patients who were diagnosed as de novo AML in Tongji Hospital from June 2012 through June 2018. A high‐throughput antibody screening for the detection of human leukocyte antigen (HLA) and its serotypes was performed in 133 newly diagnosed AML patients. PTR occurred in 11.8% of the de novo AML patients. The median age for patients with PTR was 46 years (range, 15‐70). It frequently manifested in female patients and in patients with splenomegaly, M4 subtype, c‐Kit gene mutation, and rearrangements of RUNX1‐RUNX1T1 or CBFB‐MYH11, commonly referred to as core binding factor AML (CBF‐AML). Notably, CBF‐AML was independently associated with the occurrence of PTR. PTR predominantly developed in patients who had CBF‐AML (P < .001) and in patients who further had better minimal residual disease (MRD) reduction (≥3‐log) before the second consolidation chemotherapy (P = .007). HLA‐I antibodies were detected in the serum of 9.0% of AML patients and markedly enriched in patients with PTR (P < .001) and in patients with CBF‐AML (P = .018). HLA‐B was the most frequently identified serum epitope in PTR patients. Patients with CBF‐AML had higher tendency to develop HLA‐I antibodies and PTR, which depicted novel features of PTR in AML and might provide insights into its efficient managements.

Expert consensus on the diagnosis and treatment of thrombocytopenia in adult critical care patients in China

Thrombocytopenia is a common complication of critical care patients. The rates of bleeding events and mortality are also significantly increased in critical care patients with thrombocytopenia. Therefore, the Critical Care Medicine Committee of Chinese People's Liberation Army (PLA) worked with Chinese Society of Laboratory Medicine, Chinese Medical Association to develop this consensus to provide guidance for clinical practice. The consensus includes five sections and 27 items: the definition of thrombocytopenia, etiology and pathophysiology, diagnosis and differential diagnosis, treatment and prevention.

How do I … implement diagnostic management teams in transfusion medicine?

Diagnostic management teams (DMTs) were conceptualized approximately twenty years ago in response to increasing subspecialization in medicine. DMTs are a collaboration between diagnostic experts and clinicians that aim to improve accurate and timely diagnosis and treatment of disease. Diagnostic experts provide their expertise in the increasingly complex realm of laboratory testing and interpretation of those test results to guide appropriate test utilization for individual patients. Not only can this approach improve patient care and safety, but DMTs also decrease healthcare costs by reducing unnecessary testing and potential diagnostic errors. Following the DMT construct and principles along with the 2015 National Academy of Medicine recommendations, our transfusion medicine (TM) service streamlined the workup and management of platelet refractory (PR) patients by developing and implementing a formal PR laboratory consult. The goals of this DMT and consult are to improve diagnostic management of PR patients and to decrease delays in providing these patients with appropriate and compatible platelet units. A comprehensive interpretation of test results is directly uploaded to the patient's electronic medical record (EMR), which is associated with a CPT code allowing for compensation for the PR evaluation. Herein we describe the development of and experience with the DMT since its implementation.

Platelet transfusion: Alloimmunization and refractoriness

The transfusion of platelets for both prophylaxis and treatment of bleeding is relevant to all areas of medicine and surgery. Historically, guidance regarding platelet transfusion has been limited by a lack of good quality clinical trials and so has been based largely on expert opinion. In recent years however there has been renewed interest in methods to prevent and treat hemorrhage, and the field has benefited from a number of large clinical trials. Some studies, such as platelet transfusion versus standard care after acute stroke due to spontaneous cerebral haemorrhage associated with antiplatelet therapy (PATCH) and platelets for neonatal transfusion Study 2 (PLANET-2), have reported an increased risk of harm with platelet transfusion in specific patient groups. These studies suggest a wider role of platelets beyond hemostasis, and highlight the need for further clinical trials to better understand the risks and benefits of platelet transfusions. This review evaluates the indications for platelet transfusion, both prophylactic and therapeutic, in the light of recent studies and clinical trials. It highlights new developments in the fields of platelet storage and platelet substitutes, and novel ways to avoid complications associated with platelet transfusions. Lastly, it reviews initiatives designed to reduce inappropriate use of platelet transfusions and to preserve this valuable resource for situations where there is evidence for their beneficial effect.

Immunological Features in the Process of Blood Platelet-Induced Alloimmunisation, with a Focus on Platelet Component Transfusion

Alloimmunisation to platelet antigens is not uncommon; a large number of females, having had pregnancies, developed antibodies to Human Leukocyte Antigen (HLA) moieties harboured on their foetuses' cells (inherited from the father(s)) that may conflict with further pregnancies and transfused Platelet Components occasionally. This is possible since platelets constitutionally express HLA class I molecules (though in copy numbers that consistently differ among individuals). Platelets also express HPA moieties that are variants of naturally expressed adhesion and aggregation molecules; HPA differences between mothers and foetuses and between donors and recipients explain alloimmune conflicts and consequences. Lastly, platelets express ABO blood group antigens, which are rarely immunising, however transfusion mismatches in ABO groups seem to be related to immunisation in other blood and tissue groups. Transfusion also brings residual leukocytes that may also immunise through their copious copy numbers of HLA class I (rarely class II on activated T lymphocytes, B cells, and dendritic cells). In addition, residual red blood cells in platelet concentrates may induce anti-red blood cell allo-antibodies. This short review aims to present the main mechanisms that are commonly reported in alloimmunisation. It also critically endeavours to examine paths to either dampen alloimmunisation occurrences or to prevent them.