Severe Neonatal Alloimmune Thrombocytopenia due to& ;Anti-HPA-3a

Abstract

Background and Objectives: Neonatal alloimmune thrombocytopenia is usually attributable to HPA-la antibodies. We report a case of parental platelet antigen incompatibility associated with a severe neonatal thrombocytopenia secondary to alloimmunization to HPA-3a. Materials and Methods: Platelet antibodies were detected by the monoclonal antibody-specific immobilization of platelet antigens, genotyping of the platelets by PCR, and HLA typing by serologic procedures and PCR. Results: Genotyping of maternal and paternal platelets confirmed the incompatibility in the HPA-3a system. It is noteworthy that the mother is of the HLA type DRB3*0101, is ABO-incompatible with her husband, and also has HLA class I antibodies. Conclusion: Severe neonatal thrombocytopenia associated with HPA-3a alloimmunization is infrequent and all the factors mentioned above could have played a role in the severity of the disease.

Neonatal thrombocytopenia: incidence and characterization of maternal antiplatelet antibodies by MAIPA assay

“…MAIPA was performed according to Kiefel et al (1987 ) with some modifications ( Boehlen et al , 1998 ). The test was done with the following murine antibodies: for the detection of anti‐GPIIb–IIIa antibodies, P2 and SZ22 (Immunotech, Schlieren, Switzerland) as well as PL1‐64 and PL2‐46 monoclonal antibodies (generous gift of Dr C. Kaplan, Paris), for the detection of anti‐GPIa–IIa antibodies, Gi9 (Immunotech) and for antiplatelet antibodies directed against the human platelet GPIb–IX–V complex, FMC25 (Silenus, Schlieren, Switzerland) as well as SZ1 and SZ2 (Immunotech).…”

“…To exclude false positive results due to the detection of human antibodies cross‐reacting with mouse IgG which mimic specific platelet antibodies, every positive result was checked with two methods: a sequential incubation procedure as well as a preincubation with mouse IgG‐agarose beads ( Boehlen et al , 1998 ). Determination of platelet antibody specificity in cases of alloimmunization was carried out using a panel of selected platelet donors typed for HPA‐1, HPA‐3 and HPA‐5 antigens.…”

HPA-genotyping and antiplatelet antibodies in female blood donors

“…Sera were frozen at À201C and tested subsequently in the monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay, using a pool of donor platelets, according to Kiefel et al [5][6][7] Only IgG antibodies were searched for. Monoclonal antibodies to GPIIb-IIIa (clone P2 from Immunotech, Marseille, France, PL1-64 and PL2-46, generous gifts from Dr C Kaplan, INTS, Paris, France) and GPIa-IIa (clone Gi9 from Immunotech) were used.…”

Heterogeneity of HPA‐3 alloantibodies: consequences for the diagnosis of alloimmune thrombocytopenic syndromes

“…Most frequently, immunization against HPA‐1a and ‐5b is involved in FNAIT, whereas anti‐HPA‐3a alloantibodies account for approximately 2 percent of the cases 5,6 . FNAIT due to anti‐HPA‐3a, however, is usually severe, and intracranial hemorrhage seems to be at least as frequent as in FNAIT due to anti‐HPA‐1a 7‐9 …”