HLA Class II regulation of immune response in sickle cell disease patients: Susceptibility to red blood cell alloimmunization (systematic review and meta-analysis)

Unraveling the Complex Genomic Interplay of Sickle Cell Disease Among the Saudi Population: A Case-Control GWAS Analysis

Sickle cell disease (SCD) is a severe inherited blood disorder characterized by abnormal hemoglobin (HbS) that leads to varying degrees of severity, including chronic hemolysis, episodic vaso-occlusion, and damage to multiple organs, causing significant morbidity and mortality. While SCD is a monogenic disease, its complications are influenced by polygenic factors. SCD prevalence is notably high in regions including the Middle East, with Saudi Arabia reporting significant cases, particularly in the Eastern Province. Most genetic factors associated with SCD outcomes have been identified in populations predominantly from Africa or of African ancestry. This study aims to identify genetic variants that characterize Saudi SCD patients with the potential to influence disease outcomes in this population. A multicenter case-control genome-wide association study (GWAS) was conducted involving 350 adult Saudi SCD patients and 202 healthy controls. Participants were genotyped using the Affymetrix Axiom array, covering 683,030 markers. Rigorous quality control measures were applied to ensure data integrity. Fisher's exact was used to identify genetic variants with a significant difference in allele frequency (p < 5 × 10-8). Functional annotations and regulatory functions of variants were determined using the Ensembl Variant Effect Predictor (VEP) and RegulomeDB databases. The GWAS identified numerous significant genetic variants characterizing SCD cases in the Saudi population. These variants, distributed across multiple chromosomes, were found in genes with known functional consequences. A substantial proportion of the markers were detected in the olfactory receptor cluster, TRIM family, and HBB locus genes. Many of the identified genes were reported in previous studies showing significant associations with various SCD outcomes, including hemoglobin regulation, inflammation, immune response, and vascular function. The findings highlight the genetic complexity underlying SCD and its clinical manifestations. The identified variants suggest potential molecular biomarkers and therapeutic targets, enhancing our understanding of the molecular basis of SCD in the Saudi population. This is the first genetic analysis characterizing SCD patients compared to healthy individuals, uncovering genetic markers that could serve as diagnostic biomarkers and therapeutic targets. Given the known molecular mechanisms of the detected genetic loci, these provide a foundation for precision medicine in SCD management, highlighting the need for further studies to validate these results and explore their clinical implications.

Association between HLA-DRB1*04, HLA-DQB1*03, and HLA-DQB1*06 with alloimmunization in transfusion-dependent patients with thalassemia: the first case-control study in Iran

Transfusion therapy is crucial for treating Transfusion-dependent thalassemia (TDT) patients. However, the production of Alloantibodies presents a substantial challenge for these individuals and impacts their quality of life. The Rh and Kell blood group antigens are particularly susceptible to alloantibody development. This study aims to establish the correlation between HLA-DRB1*04, HLA-DQB1*03, and HLA-DQB1*06 alleles and alloimmunzation in thalassemia patients from Iran. 98 thalassemic patients were recruited for this study (49 alloimmunized and 49 non-alloimmunized). Alloimmunized patients developed Rh and Kell specificities alloantibodies. The two groups were compared based on the results of HLA-DRB1 and HLA-DQB1 genotyping conducted using Sequence-Specific Primers (SSP-PCR). The findings from the antibody screening revealed that the predominant alloantibody detected was Anti-K (95.9%), Anti-E (65.3%), Anti-C (30.6%), Anti-D (28.6%), Anti-c (10.2%), Anti-e (2%), and Anti-k (2%). There was a notable difference in HLA-DQB1*03 between alloimmunized and non-alloimmunized groups, 41.8% vs. 58.2%, respectively. (iP = 0.001, OR = 0.135, CI = 0.036-0.499). There was not any notable relationship between HLA-DRB1*04 and HLA-DQB1*06 alleles and alloimmunization. Our findings indicate that HLA-DQB1*03 may have a protective role in preventing alloantibody production. Thus, HLA-typing, particularly focusing on DQB1*03, can significantly enhance the screening process, leading to improved blood transfusion management, reduced rejection of hematopoietic stem cell transplantation, and minimized blood transfusion complications.

Impact of human leucocyte antigen class II polymorphism on anti-red blood cell antibody development: Correlations and indications

BACKROUND AND OBJECTIVES

Blood transfusion therapy is vital for many patient groups. They can cause many complications, and the development of anti-red blood cell (RBC) antibodies is of significant importance. Molecules of class II human leucocyte antigens (HLA) are one of the several factors that influence antibody development in patients.

MATERIALS AND METHODS

In this study, we investigated 108 patients who developed antibodies against different erythrocyte antigens and 115 patients on multiple transfusion therapies who did not develop anti-RBC antibodies. The HLA loci HLA-DRB1 and HLA-DQB1 were typed using commercial molecular assays routinely used in HLA laboratories.

RESULTS

An increased frequency of the HLA-DRB1*04 allele group was observed in patients who developed antibodies. Additionally, HLA-DRB1*09 was also significant for anti-E development and in patients with multi-specific alloimmunization. It was found that the HLA-DRB1*07 allele group is associated with antibodies to antigents of the Rh and MNS systems but also lacks an association with anti-K development. The HLA-DRB1*11 and -DRB1*01 allele groups displayed a protective mechanism for anti-E development, similar to that of HLA-DQB1*02 for anti-K.

CONCLUSION

There is an association between various HLA class II alleles and anti-RBC development.

Association of HLA-DRB1 alleles with anti-D alloimmunization in RhD negative pregnant women in India

BACKGROUND

Human leukocyte antigen (HLA) restriction plays an important role in the susceptibility to alloimmunization against red blood cell (RBC) antigens. The prevalence of anti-D alloimmunization in RhD negative pregnancy is still quite high in our population. Thus, we planned this study to determine the association of HLA-DRB1 alleles with anti-D alloimmunization in RhD negative pregnant women.

MATERIAL AND METHODS

RBC antibody screen (ABS) was performed for RhD negative pregnant women attending the antenatal clinic our institute. Those with a negative result were included in the 'non-alloimmunized' (NAL) group ('Control' group), while those with anti-D alloantibody on performing antibody identification were included in the alloimmunized (AL) group of the study (n = 50 each). ABS and identification were done using column agglutination technique. The HLA-DRB1 typing was done by Luminex based reverse sequence specific oligonucleotide probing (SSOP) using commercial kits. The HLA-DRB1 allele frequency was compared in both the groups.

RESULTS

There was a significant difference between the two groups in terms of gravida (p < 0.001) and history of anti-D immunoprophylaxis (p < 0.001). The frequency of HLA-DRB1*03 and HLA-DRB1*04 alleles was significantly higher in the AL group than the NAL group: 40 % versus 18 % [Odds Ratio (OR): 3.04, 95 % CI: 1.21-7.6; p = 0.015] for HLA-DRB1*03 alleles and 18 % versus 4 % (OR: 5.27, 95 % CI: 1.08-25.78, p = 0.025) for HLA-DRB1*04 alleles.

CONCLUSION

The frequency of HLADRB1*03 and HLADRB1*04 alleles was significantly higher in RhD negative pregnant women alloimmunized with anti-D alloantibody.

HLA-F and LILRB1 Genetic Polymorphisms Associated with Alloimmunisation in Sickle Cell Disease

Red blood cell (RBC) transfusion remains a critical component in caring for the acute and chronic complications of sickle cell disease (SCD). Patient alloimmunisation is the main limitation of transfusion, which can worsen anaemia and lead to delayed haemolytic transfusion reaction or transfusion deadlock. Although biological risk factors have been identified for immunisation, patient alloimmunisation remains difficult to predict. We aimed to characterise genetic alloimmunisation factors to optimise the management of blood products compatible with extended antigen matching to ensure the self-sufficiency of labile blood products. Considering alloimmunisation in other clinical settings, like pregnancy and transplantation, many studies have shown that HLA Ib molecules (HLA-G, -E, and -F) are involved in tolerance mechanism; these molecules are ligands of immune effector cell receptors (LILRB1, LILRB2, and KIR3DS1). Genetic polymorphisms of these ligands and receptors have been linked to their expression levels and their influence on inflammatory and immune response modulation. Our hypothesis was that polymorphisms of HLA Ib genes and of their receptors are associated with alloimmunisation susceptibility in SCD patients. The alloimmunisation profile of thirty-seven adult SCD patients was analysed according to these genetic polymorphisms and transfusion history. Our results suggest that the alloimmunisation of SCD patients is linked to both HLA-F and LILRB1 genetic polymorphisms located in their regulatory region and associated with their protein expression level.

Asian-type DEL (RHD*DEL1) with an allo-anti-D: A paradoxical observation in a healthy multiparous woman

BACKGROUND

The DEL phenotype is the D variant expressing the least amounts of D antigen per red cell. Asian-type DEL (RHD:c:1227G > A) is the most prevalent DEL in East Asia without any anti-D alloimmunization reported before. We investigated the first observation of an anti-D in any DEL phenotype, reported in the Japanese language at a 1987 conference, only 3 years after the discovery of DEL.

METHODS

We contacted the proband 35 years after the initial report. Standard hemagglutination, adsorption/elution, and flow cytometry tests were performed, as was nucleotide sequencing for the RHD, RHCE, and HLA class I and class II genes.

RESULTS

The healthy multiparous Japanese woman, a regular blood donor, still had the anti-D of titer 8 representing an alloantibody by standard serologic methods. Unexpectedly, she carried an Asian-type DEL without any additional RHD gene variation. All 12 HLA alleles identified were known in the Japanese population. Interestingly, one of her HLA-DRB1 and a variant of her HLA-DQB1 alleles had previously been associated with anti-D immunization.

CONCLUSION

We described an allo-anti-D, maintained for more than three decades, in an Asian-type DEL. The combination of two implicated HLA alleles were rare and could have contributed to the anti-D immunization. Continued monitoring of anti-D immunization events in patients with DEL is warranted, and we discuss possible mechanisms for further study. As only this single observation has been recognized in the last 35 years, the current recommendation is affirmed: Individuals with Asian-type DEL should be treated as Rh D-positive for transfusion and Rh immune prophylaxis purposes.

Investigation of variables affecting the immunogenicity of blood group antigens using a calculation formula

Previous studies on the immunogenicity of blood group antigens have utilized a formula incorporating antigen frequencies and relative frequencies of unexpected antibodies to the corresponding antigens. This study was aimed at investigating other variables potentially affecting the estimation of immunogenicity using this formula. We examined the effect of multiple transfusions, as there are more chance for a recipient to receive repeated transfusions rather than only once; the effect of antigen density, which may vary depending on homozygote/heterozygote; and the effect of unreliability of the observed frequency of rare antibodies and antigens. For multiple transfusions, the expected antibody frequency increased as the number of transfusions increased. For antigen density, the immunogenicity was falsely low for the low-prevalence antigen, and this tendency intensified as the effect of antigen density increased. Expected antibody frequencies were significantly affected by the uncertainties caused by estimation of small numbers. This study showed that the effects of various factors on the immunogenicity of blood group antigens depended on the antigen frequency. Estimating the immunogenicity of blood group antigens requires acknowledging the diverse factors that can affect it and interpreting the findings with caution.

Comparison of the conventional tube and erythrocyte-magnetized technology in titration of red blood cell alloantibodies

BACKGROUND

Erythrocyte alloantibodies are mainly produced after immune stimulation, such as blood transfusion, pregnancy, and transplantation, and are the leading causes of severe hemolytic transfusion reactions and difficulty in blood grouping and matching. Therefore, antibody screening is critical to prevent and improve red cell alloantibodies. Routine tube assay is the primary detection method of antibody screening. Recently, erythrocyte-magnetized technology (EMT) has been increasingly used in clinical practice. This study intends to probe the application and efficacy of the conventional tube and EMT in red blood cell alloantibody titration to provide a reference for clinical blood transfusion.

AIM

To investigate the application value of conventional tube and EMT in red blood cell alloantibody titration and enhance the safety of blood transfusion practice.

METHODS

A total of 1298 blood samples were harvested from blood donors at the Department of Blood Transfusion of our hospital from March 2021 to December 2022. A 5 mL blood sample was collected in tubing, which was then cut, and the whole blood was put into a test tube for centrifugation to separate the serum. Different red blood cell blood group antibody titers were simultaneously detected using the tube polybrene test, tube antiglobulin test (AGT), and EMT screening irregular antibody methods to determine the best test method.

RESULTS

Simultaneous detection was performed through the tube polybrene test, tube AGT and EMT screening irregular antibodies. It was discovered that the EMT screening irregular antibody method could detect all immunoglobulin G (IgG) and immunoglobulin M (IgM) irregular antibodies, and the results of manual tube AGT were satisfactory, but the operation time was lengthy, and the equipment had a large footprint. The EMT screening irregular antibody assay was also conducted to determine its activity against type O Rh (D) red blood cells, and the outcomes were satisfactory. Furthermore, compared to the conventional tube method, the EMT screening irregular antibody method was more cost-effective and had significantly higher detection efficiency.

CONCLUSION

With a higher detection rate, the EMT screening irregular antibody method can detect both IgG and IgM irregular antibodies faster and more effectively than the conventional tube method.

Alloimmunisation against red blood cells in sickle cell disease: transfusion challenges in high-income and low-income countries

Sickle cell disease is the most frequent inherited disorder in sub-Saharan Africa and in many high-income countries (HICs). Transfusion is a key element of treatment, but it results in high rates of alloimmunisation against red blood cell antigens and post-transfusion haemolysis, which can be life-threatening in severe cases. The prevention of alloimmunisation is, therefore, an important issue in both HICs and in low-income countries (LICs). In HICs, the main reason for high alloimmunisation rates is blood group disparity between blood donors, who are mostly of European descent, and the patients, who are mostly of African descent. However, alloimmunisation rates also remain high in sub-Saharan Africa despite the homogeneity of blood group antigen frequencies between donors and patients; this occurrence is probably due to matching strategies limited to ABO blood group and RhD. However, other possible underlying causes of alloimmunisation have also been suggested, with each cause affecting HICs and LICs in different ways-eg, the immunogenetic and inflammatory status of the patient and the characteristics of the red blood cell products. In this Viewpoint, we discuss the available data and hypotheses that potentially account for the association of sickle cell disease with high rates of alloimmunisation in both settings, HICs and LICs (focusing particularly on sub-Saharan Africa), and the challenges faced by HICs and LICs to improve prevention of alloimmunisation.