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【Objective】 To investigate the frequency of platelet antibodies in voluntary blood donors and patients in Zhongshan, Guangdong Province, and to study the specificity and cross-matching of platelet antibodies. 【Methods】 Platelet antibodies of blood donors and patients were screened by solid-phase immunoadsorption (SPIA), rechecked by flow cytometry (FCM), and antibody specificity was identified by PakPlus enzyme immunoassay, and platelet cross-matching was simulated by SPIA. 【Results】 A total of 1 049 blood donor samples and 598 patient samples were tested, with 6 (0.57%) and 49 (8.19%) samples positive for SPIA,respectively(P<0.05); In SPIA positive samples, the positive concordance rate of FCM in blood donors and patients was 100% vs 95%, and that of enzyme immunoassay was 100% vs 88%. Among the initial screening positive samples of blood donors, 5 were anti-HLA Ⅰ antibodies, accounting for 83%, and 1 was anti CD36 antibody, accounting for 17%, with an incidence rate of 0.10%. Among the 14 samples of enzyme immunoassay positive patients, 2 were anti-GP Ⅱb/Ⅲa, 1 was anti-GP Ⅱa/Ⅱa, 8 were anti HLA Ⅰ, and 3 were mixed antibodies (HLA Ⅰ, GP Ⅱb/Ⅲa, GP Ⅰa/Ⅱa). According to the types of antibodies, HLA Ⅰ antibodies were the most common, accounting for 65% (11/17), followed by HPA related anti GP, accounting for 35% (6/17). The majority of patients had a platelet antibody positive typing rate below 30%, accounting for 71.4% (10/14). 【Conclusions】 The positive rate of platelet antibody of patients in Zhongshan area is significantly higher than that of voluntary blood donors, and most of them are anti-HLA Ⅰ and anti-GP, and the incidence of anti-CD36 is extremely low. Therefore, it is necessary to establish a known platelet antigen donor bank, and at the same time, carry out platelet antibody testing and matching of patients, which is helpful to solve the issue of platelet transfusion refractoriness.

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BACKGROUND: CD36-deficient individuals may produce anti-CD36 antibodies through antigenic exposure to CD36, in situations including blood transfusions. Therefore, allogeneic hematopoietic stem cell transplantation (HSCT) from CD36-positive donors to CD36-negative patients remains a challenge. CASE REPORT: A 64-year-old man with acute myeloid leukemia became refractory to platelet transfusions during chemotherapy. Anti-CD36 antibodies without anti-HLA antibodies were detected in serum, and the absence of CD36 expression on platelets and monocytes confirmed type I CD36 deficiency. The patient achieved complete remission, and received maintenance therapy with CD36-negative platelet transfusions. However, he relapsed soon afterward, and thus underwent peripheral blood stem cell transplantation (PBSCT) from a CD36-positive unrelated donor. The anti-CD36 antibody titer had decreased before the transplant, and the PBSCT-course was uneventful. The patient has been well without any complications associated with CD36 status mismatch. DISCUSSION: The few reports of allogeneic HSCT in patients with CD36 deficiency have suggested that anti-CD36 antibodies could be involved in several post-transplant complications, such as delayed platelet recovery, transfusion refractoriness, and transfusion-related acute lung injury. Our present case confirmed that stem cell transplantation from CD36-positive donors to negative patients is feasible, when it includes careful prior assessment of anti-CD36 antibody titers and interventions to attenuate them.

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CD36 is a multifunctional receptor expressed on the surface of many cell types. Among healthy individuals, CD36 may be absent on platelets and monocytes (type I deficiency) or platelets alone (type II deficiency). However, the exact molecular mechanisms underlying CD36 deficiency remain unclear. In this study, we aimed to identify individuals with CD36 deficiency and investigate the molecular basis underlying it. Blood samples were collected from platelet donors at Kunming Blood Center. Platelets and monocytes were isolated and CD36-expression levels were analyzed using flow cytometry. DNA from whole blood and mRNA isolated from monocytes and platelets of individuals with CD36 deficiency were analyzed using polymerase chain reaction (PCR) testing. The PCR products were cloned and sequenced. Among the 418 blood donors,7 (1.68%) were CD36 deficient: 1 (0.24%) with type I deficiency and 6(1.44%) with type II deficiency. Six heterozygous mutations occurred, including c.268C>T (in type I individuals), c.120 + 1 G>T, c.268C>T, c.329_330del/AC, c.1156 C>T, c.1163A>C, and c.1228_1239del/ATTGTGCCTATT (in type II individuals). Mutations were not detected in one type II individual . At the cDNA level, only mutant, but not wild-type, transcripts were detected in the platelets and monocytes of type I individual. In type II individuals, only mutant transcripts were found in platelets, whereas monocytes possessed wild-type and mutant transcripts. Interestingly, only alternative splicing transcripts were observed in the individual without mutation. We report the incidence rates of type I and II CD36 deficiencies among platelet donors in Kunming. Molecular genetic analyses of DNA and cDNA demonstrated that homozygous mutations on the cDNA level in platelets and monocytes or platelets alone identified type I and II deficiencies, respectively. Furthermore, alternatively spliced products also potentially contribute to the mechanism of CD36 deficiency.

What is the context? Healthy individuals may lack CD36 on platelets and (or) monocytes, which are defined as Type I and Type II CD36 deficiency. These individuals could develop anti-CD36 antibodies associated with immune-mediated disorders. However, the mechanism underlying the CD36 deficiency is still unclear. In this study, we reported the incidence of CD36 deficiency in Kunming platelet donors and found the new molecular basis of CD36 deficiency individuals.What's new? Molecular genetic analysis of cDNA derived from type I subjects showed the presence of mutant transcript only, both in platelets and monocytes. In type II subjects, platelets only carry mutant transcript, whereas monocytes possessed both wild-type and mutant transcripts. Furthermore, we found that alternatively spliced product of CD36 transcript could also contribute to the mechanism of CD36 deficiencies.What's the impact? Our finding indicates that analysis of CD36 at cDNA level is mandatory to verify different forms of CD36 deficiencies. This information may help us to understand the development of anti-CD36 antibodies in CD36 deficient individuals.

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【Objective】 To search compatible and suitable platelets for platelet transfusion refractoriness (PTR) patient caused by compound antibodies against HLA and CD36. 【Methods】 ELISA method was used to detect the antibody against platelet antigens and the specificity of HLA-I antibody in PTR patients. The specificity of HLA-I antibody and corresponding epitopes of patients were analyzed using MATCH IT! and HLA Matchmaker software. The HLA genotype of both donor and patient was obtained by HLA-SSO method. Compatible or suitable donor platelets for PTR patients were searched through cross-reactive group (CREG) of HLA-I and HLA epitope-matched approach (Eplet). The matching degree was identified using monoclonal antibody-specific immobilization of platelet antigens (MAIPA) and the platelet suspension immunofluores-cence test (PIFT). Finally, the transfusion effect was evaluated according to the corrected count increment (CCI). 【Results】 Compound antibodies against both CD36 and HLA-I antigens were detected in two PTR patients, and their phenotype of CD36 was conformed to be type I deficient. Through LSA testing, high-frequency of HLA -I antibodies was found in these two patients, and the panel reactive antibody in patients 1 and 2 was 56% (54/96) and 53% (51/96), respectively. According to HLA-CREG and Eplet matching strategies, one donor of grade C-matching with patient 1 and one donor of grade D-matching with patient 2 were screened from the CD36 deficiency donor bank, respectively. And the selected donors avoided the antigen of HLA-I antibody epitope. These results of MAIPA and PIFT also confirmed that no immune response was detected between the patient and the donor. And a CCI of >4.5 within 24 hour of transfusion of compatible platelets was obtained in patient 2. 【Conclusion】 For PTR patients caused by HLA and CD36 compound antibodies, a combination strategy including serological cross-matching, HLA-CREG and Eplet approach should be used to select the CD36 deficient donor platelets which evaded the antigen corresponding to HLA-I antibodies and had the compatible HLA epitopes.

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【Objective】 To study the incidence and specificity of platelet antibody in blood donors in Suzhou, analyze the distribution characteristics of platelet antibody in blood donors in this area, and explore the significance of platelet antibody detection in blood donors to reduce the adverse reactions toplatelet transfusion in clinical. 【Methods】 Platelet antibody detection was performed in 2178 blood donors in this area by solid-phase immunosorbent assay. The antibody specificity of the positive samples was analyzed by commercial kit, and the anti-CD36 antibody positive samples were further identified by flow cytometry and gene sequencing. 【Results】 Twelve positive samples were detected by platelet antibody screening, with a positive rate of 0.55%(12/2 178), including 5 males (0.33%, 5/2 178)and 7 females(1.06%, 7/2 178). Among the positive samples, anti-HLA-Ⅰ antibody was identified in 2 cases, anti-CD36 antibody in 1 case, and the antibody specificity was not identified in the other 9 cases. In one case, the positive rate of anti-HLA-Ⅰ antibody PRA was 31.31%(31/ 99), which was mainly specific to anti-B15, anti-B35 and anti-B40. The positive rate of anti-HLA-Ⅰ antibody PRA in the other case was 45.45%(45/ 99), which was mainly specific to anti-A2, anti-A11, anti-A24, anti-A29, anti-A33, anti-A66, anti-B15 and anti-B35. The blood donor with anti-CD36 antibody was type I CD36 deficiency, and 329_330delAC mutation occurred in exon 5. 【Conclusion】 Through antibody screening and specificity identification, the positive rate of platelet antibody in females was significantly higher than that in males(P<0.05). In addition to the common anti-HLA-I antibodies, anti-CD36 antibody was also detected in type I CD36 deficient blood donor. Therefore, the detection of platelet antibodies in blood donors is of certain clinical significance to reduce the adverse reactions to blood transfusion caused by antibodies in platelet products.

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OBJECTIVES: In the present study, we asked whether anti-CD36 antibodies impair the maturation of erythropoietic stem cells to mature red blood cells (RBCs), leading to anaemia and hydrops fetalis (HF). BACKGROUND: Recent studies have shown the importance of anti-CD36 antibodies in the development of Fetal/Neonatal Alloimmune Thrombocytopenia (FNAIT). In comparison to other types of antibody-mediated FNAIT, anti-CD36 antibodies are frequently associated with anaemia and HF. As mature RBCs do not express CD36, the reason for this phenomenon is currently not fully understood. MATERIAL AND METHODS: A case of FNAIT with signs of HF was characterised in this study. Maternal anti-CD36 antibodies were isolated by an absorption/elution approach. We cultured haematopoietic stem cells (HSCs) with purified anti-CD36 antibodies, and the formation of burst-forming unit-erythroid and colony-forming unit-erythroid (CFU-E/BFU-E) cells was analysed. Apoptosis of HSCs was also investigated. RESULTS: Analysis of the mother showed type-1 CD36 deficiency. Anti-CD36 antibodies were found in maternal serum, as well as on fetal platelets, by ELISA, and the specificity of these antibodies was further substantiated by flow cytometry. In comparison to control IgG, incubation of HSCs with purified anti-CD36 antibodies led to a significant reduction in CFU-E/BFU-E cell formation, and this result was associated with an increased number of apoptotic CD34+ erythroid/myeloid precursor cells. Administration of intra-uterine transfusion with washed RBCs was effective in improving fetal anaemia. CONCLUSIONS: Anti-CD36 antibodies may cause anaemia and trigger HF through apoptosis of CD34+ erythroid/myeloid precursor cells. However, the contribution of other cells must also be taken into account.

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Cases of CD36 deficiency are not rare in Asian populations, foetal and neonatal alloimmune thrombocytopenia (FNAIT) caused by anti-CD36 isoantibodies appears more frequent than other HPA alloantibodies. However, little is known about the treatment of anti-CD36 mediated FNAIT in this region. A Chinese male foetus, whose mother had a history of multiple intrauterine foetal demise and/or hydrops, was diagnosed with severe FNAIT at 27 weeks of gestational age. Immunological analysis revealed total absence of CD36 on platelets and monocytes from mother, caused by a 329-330delAC mutation of the CD36 gene. Anti-CD36 and anti-HLA class I antibodies were detected in the maternal serum, whereas only anti-CD36 isoantibodies were detectable in the foetal blood sample. Serial intrauterine transfusions with red blood cells (RBC) and platelets from a CD36null donor were performed to improve the severe anaemia and thrombocytopenia. The baby (2250 g; Apgar scores 10) was delivered vaginally at 32 weeks of gestation with normal haemoglobin (186 g/L) but low platelet count (48 × 109/L). After 2 days the platelet count rose to 121 × 109/L. This report suggests that intrauterine transfusions with compatible RBC and CD36null platelets are useful in preventing the deleterious clinical effects of anti-CD36-mediated severe FNAIT.

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Immunization against human platelet alloantigens (HPAs) is associated with a number of clinical complications. The detection and identification of clinically relevant platelet antibodies are important for the diagnosis and management of patients affected with immune-mediated thrombocytopenias. Human platelet alloantigen frequencies and the characteristics of antiplatelet antibodies vary widely between ethnic groups. Since 2008, the importance of platelet immunology in the field of transfusion medicine has gained greater recognition by clinical laboratories in China. Laboratories in China have established and improved methods for platelet antibody detection and HPA genotyping techniques, which are used for the diagnosis of alloimmune platelet disorders in clinic and research environments. Research has revealed the frequencies of HPA alleles in different Chinese ethnic groups and compared the differences in HPA gene frequencies between the Chinese Han and other ethnic groups of the world. Production of anti-CD36 isoantibodies is an important risk factor for immune-mediated thrombocytopenia in the Chinese population. Advances in research and clinical application of platelet immunology have significantly improved the clinical diagnosis, treatment including transfusion support, and prevention of alloimmune platelet disorders in the Chinese population.

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