Antibodies against human CD36 are responsible for several immune-mediated disorders. The detection of anti-CD36 antibodies using the standard monoclonal antibody (mAb) immobilization of platelet antigens (MAIPA) assay is hampered by a high frequency of false-negative results, most likely due to competitive inhibition of the mAb used as the capture antibody. We generated a panel of mouse mAbs against CD36 and seven hybridomas (GZ-3, GZ-13, GZ-70, GZ-143, GZ-413, GZ-507, and GZ-608), which were selected for MAIPA assays, as they reacted with mouse and human CD36. Fourteen anti-CD36 sera were assayed; all of which showed a positive reaction in a PakPlus (Immucor GTI Diagnostics, Inc., Waukesha, WI, USA) ELISA-based screening (optical density: 0.257–2.292). When the reference anti-CD36 mAb FA6-152 was used in the MAIPA assay, only 6/14 (42.9%) sera displayed a positive reaction. In contrast, anti-CD36 antibodies were detected in 13/14 (92.9%) sera when GZ-70 and GZ-608 mAbs were used. This significant improvement resulted in the identification of anti-CD36 antibodies by an antigen capture assay. Since patient’s platelets possibly carrying rare native antigens are used, this method will facilitate the identification of new platelet antibodies against CD36 that are involved in immune-mediated thrombocytopenia and other diseases, such as transfusion-related acute lung injury.

Objective: To explore the role of the c.598G>A mutation of the ITGB3 gene in the occurrence of fetal and neonatal alloimmune thrombocytopenia (FNAIT) through its expression in vitro. Methods: The platelet antibodies in the sera of the affected neonate and her mother were detected using commercial enzyme-linked immunosorbent assay (ELISA), solid-phase agglutination, flow cytometry and the gold standard monoclonal antibody-specific immobilization of platelet antigens (MAIPA). The common human platelet antigen (HPA) genotypes of the neonate and her parents were obtained using the HPA-SSP method. The presence of mutations was analyzed by sequencing the exons of the ITGB3 and ITGA2B genes. The target gene of ITGB3 was obtained by PCR amplification using the existing human platelet cDNA. The wild-type ITGB3 eukaryotic expression vector was constructed by TA cloning technology. The 598G>A mutant ITGB3 eukaryotic expression vector was obtained by point mutation, and the plasmid DNA was co-transfected with that of ITGA2B (αⅡb) into HEK293 cells. The transfected cells stably expressing GP Ⅱb/Ⅲa were screened and obtained. The expression of GP Ⅱb/Ⅲa in 598G>A mutant transfected cells and the presence of antibodies against this mutation in the serum of mother were detected by flow cytometry and MAIPA. Results: Antibodies against HLA-class Ⅰ and GP Ⅱb/Ⅲa glycoproteins were detected in the serum of the neonate's mother, and subsequent HLA antibody-specific testing confirmed the presence of antibodies against HLA-B 57∶01 and A 02∶05. ITGB3 sequencing showed that the neonate and her father carried the c.598G>A point mutation, which results in the change of glutamate to lysine at position 200. Antibodies against GP Ⅱb/Ⅲa glycoproteins were not detected using constructed c.598G>A mutant transfected cells reacted with the maternal serum. Conclusion: The in vitro expression and analysis of the ITGB3 c.598G>A mutation did not support a role for this mutation in the pathogenesis of FNAIT. The establishment of this method facilitates the discovery of new platelet low-frequency antigens, and provides a theoretical foundation for the detection of antibodies against platelet antigens associated with patients with adverse pregnancy and childbirth histories.

Objective: To explore the role of the c.598G>A mutation of the ITGB3 gene in the occurrence of fetal and neonatal alloimmune thrombocytopenia (FNAIT) through its expression in vitro. Methods: The platelet antibodies in the sera of the affected neonate and her mother were detected using commercial enzyme-linked immunosorbent assay (ELISA), solid-phase agglutination, flow cytometry and the gold standard monoclonal antibody-specific immobilization of platelet antigens (MAIPA). The common human platelet antigen (HPA) genotypes of the neonate and her parents were obtained using the HPA-SSP method. The presence of mutations was analyzed by sequencing the exons of the ITGB3 and ITGA2B genes. The target gene of ITGB3 was obtained by PCR amplification using the existing human platelet cDNA. The wild-type ITGB3 eukaryotic expression vector was constructed by TA cloning technology. The 598G>A mutant ITGB3 eukaryotic expression vector was obtained by point mutation, and the plasmid DNA was co-transfected with that of ITGA2B (αⅡb) into HEK293 cells. The transfected cells stably expressing GP Ⅱb/Ⅲa were screened and obtained. The expression of GP Ⅱb/Ⅲa in 598G>A mutant transfected cells and the presence of antibodies against this mutation in the serum of mother were detected by flow cytometry and MAIPA. Results: Antibodies against HLA-class Ⅰ and GP Ⅱb/Ⅲa glycoproteins were detected in the serum of the neonate's mother, and subsequent HLA antibody-specific testing confirmed the presence of antibodies against HLA-B 57∶01 and A 02∶05. ITGB3 sequencing showed that the neonate and her father carried the c.598G>A point mutation, which results in the change of glutamate to lysine at position 200. Antibodies against GP Ⅱb/Ⅲa glycoproteins were not detected using constructed c.598G>A mutant transfected cells reacted with the maternal serum. Conclusion: The in vitro expression and analysis of the ITGB3 c.598G>A mutation did not support a role for this mutation in the pathogenesis of FNAIT. The establishment of this method facilitates the discovery of new platelet low-frequency antigens, and provides a theoretical foundation for the detection of antibodies against platelet antigens associated with patients with adverse pregnancy and childbirth histories.

【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.