Prevalence of Alloimmunization to Human Platelet Antigen Glycoproteins and Human Leucocyte Antigen Class I in β Thalassemia Major Patients in Western India

Human leukocyte antigen immunization in transfusion-dependent Moroccan patients with beta-thalassemia major: prevalence and risk factors

INTRODUCTION

Beta-thalassemia major patients need a regular blood transfusion to have an initial normal growth. However, these patients have an increased risk of developing alloantibodies. Our main goal was to study HLA alloimmunization in Moroccan Beta-thalassemia patients by confronting it with transfusion and demographic criteria, exploring the involvement of HLA typing profile in the development of HLA antibodies and in turn determining risk factors for their development.

METHODS

The study consisted of 53 Moroccan pediatric patients with Beta-thalassemia major. Screening for HLA alloantibodies was performed using Luminex technology Whereas HLA genotyping was done with sequence-specific primers (PCR-SSP).

RESULTS

In this study, 50.9% of patients have been identified as positive for HLA antibodies, with 59.3% having both HLA Class I and Class II antibodies. A significant increase frequency of DRB1*11 allele was revealed in non-immunized patients (34.6% vs. 0%, p = 0.001). Our results also revealed that the majority of our HLA immunized patients were women (72.4% vs. 27.6%, p = 0.001), and transfused with more than 300 units of RBC units (66.7% vs. 33.3%, p = 0.02). There were statistically significant differences when comparing these frequencies.

CONCLUSIONS

This paper revealed that the transfusion dependent Beta-thalassemia major patients are exposed to risk of developing HLA antibodies following transfusions with leukoreduced RBC units. The HLA DRB1*11 was a protective factor against HLA alloimmunization in our beta-thalassemia major patients.

Major histocompatibility complex (MHC) antigens polymorphism and alloimmunization study in thalassemia patients with febrile non-hemolytic transfusion reaction (FNHTR)

OBJECTIVES

HLA alloimmunization is one of the most troublesome consequence of regular transfusion which is itself a mainstay measure to provide longevity to the thalassemia patients. Febrile non-hemolytic transfusion reaction (FNHTR) is one of the most common complication which might be related to the HLA alloimmunization. Here, we studied the HLA antigenic system and alloimmunization rate in the Iranian β-thalassemia patients who suffered from FNHTR compare to the β-thalassemia patients without FNHTR.

MATERIALS & METHODS

Total of 60 β-thalassemia patients with FNHTR (case group) and 20 β-thalassemia patients without FNHTR (control group) randomly have been selected and enrolled in the study. All were tested for HLA-A and -B loci by PCR-SSP method and also for the presence of anti-lymphocyte antibodies by LIFT method. Comparisons between two groups were performed by Pearson's χ2 test.

RESULTS

Totally, a significant predominance was noted for two HLA alleles, HLA-A*24 (P = 0.029) and B*55 (P = 0.034) which have higher prevalence in control group. Although no significant association was found between the presence of anti-leukocyte antibodies and the development of FNHTR, the HLA-A*32 (P = 0.047) allele was considered as possible genetic markers in the susceptibility to the development of anti-leukocyte antibodies.

CONCLUSION

Here some evidences about the possible role of HLA polymorphism in susceptibility to FNHTR are provided. Those results indicated that HLA-A*24 and HLA-B*55 might play protective role on inducing FNHTR in β-thalassemia patients. Further studies which investigate the allele level of HLA-I alongside with specific reactivity of HLA-I antibodies might reveal more deep data about these phenomena.

Frequency of Platelet Crossmatch Positivity and Predictive Value for Poor Platelet Increment Among Paediatric Oncohaematology Patients in India

Immune platelet destruction is a significant cause for platelet refractoriness. The platelet crossmatch-a solid phase red cell adherence assay utilizes donor platelets and patient serum to assess compatibility and appears to be a feasible option in resource constrained settings. This study was done to evaluate the frequency of platelet crossmatch positivity among Paediatric Oncohaematology patients and also to assess whether a positive crossmatch is predictive of unsuccessful platelet transfusions in this group of patients. Paediatric Oncohaematology patients who received platelet transfusions between March 2013 and September 2013 were included in the study. The pre-transfusion patient sample and a segment from the transfused donor unit were used for performing the platelet crossmatch. A blood sample was collected one hour after the transfusion to assess post-transfusion platelet count. Corrected count increment (CCI) was calculated using the standard formula. CCI ≤ 7500/µL/m²/10¹¹ was considered evidence of an unsuccessful transfusion. Seventy-three platelet crossmatches were performed for 69 patients, of which 30 patient samples (41%) showed crossmatch positivity. 25 (89.2%) of 28 unsuccessful transfusions showed crossmatch positivity, and 40 (88.9%) of 45 successful transfusions showed negative crossmatches (p = 0.03). Crossmatch positivity among transfusion dependent Paediatric Oncohaematology patients was as high as 42%, when ABO matched platelet units were allocated without further testing. Our results indicate that this test may be a reliable tool to select compatible platelet units and an effective intervention in the management of patients at risk of immune platelet refractoriness.

Class I and II HLA antibodies in pediatric patients with thalassemia major

BACKGROUND

HLA alloimmunization is a potential complication of red blood cell (RBC) transfusion with detrimental consequences for future organ or hematopoietic stem cell transplantation.

STUDY DESIGN AND METHODS

The study aimed to determine the prevalence and specificity of HLA antibodies among pediatric patients with thalassemia major (TM) and antibody changes over time while on leukoreduced chronic transfusion therapy. HLA antibodies were measured at two or more time points in children and young adults ages 3 to 21 years with TM. HLA Class I and II antibodies were measured by FlowPRA screening. Positive screening assays were confirmed with LabScreen single-antigen bead assays for antibody specificity.

RESULTS

HLA antibodies were detected in 10 of 19 (53%) subjects: seven of 19 (37%) with HLA Class I and II antibodies, two of 19 (11%) with only HLA Class I antibodies, and one of 19 (5%) with only HLA Class II antibodies. Subjects with HLA antibodies were older (14.6 years vs. 7.1 years, p = 0.05), predominantly male (80%), and more likely to have a remote history of nonleukoreduced transfusions (p = 0.057). Median time between testing was 3.7 years. De novo HLA antibodies were detected in two of 11 patients who initially had negative panel-reactive antibody screens, while one subject lost detection of Class II antibody. Two of seven patients with HLA antibodies had antibodies to self-HLA.

CONCLUSION

HLA antibodies have a high prevalence in TM patients and may be associated with nonleukoreduced transfusions and older age. For such patients, antibody identification will be useful if subsequent organ or stem cell transplantation is needed.