Molecular typing of human platelet antigens in immune thrombocytopenia patients in northern Brazil

Abstract

BackgroundImmune thrombocytopenia is an immune disease characterized by thrombocytopenia and bleeding due to platelet antibodies against platelet membrane glycoproteins. Human platelet antigens are derived from polymorphisms of these glycoproteins. The aim of this study was to investigate human platelet antigen frequencies in immune thrombocytopenia patients from the state of Amazonas, Brazil and investigate the potential association between specific antigens and risk for immune thrombocytopenia.MethodHuman platelet antigen typing was performed by BeadChip technology to determine allelic variants of 11 systems (HPA-1 to HPA-9, HPA-11 and HPA-15). Thirty-six patients (8 male and 28 female) with a median age of 34 years (range: 9–69 years) were evaluated and compared with data from Amazonas blood donors.ResultsPlatelet counts varied from 3 to 98 × 109/L. The allele frequencies were 0.944 for HPA-1a, 0.056 for HPA-1b, 0.847 for HPA-2a, 0.153 for HPA-2b, 0.555 for HPA-3a, 0.444 for HPA-3b, 0.805 for HPA-5a, 0.222 for HPA-5b, 0.9975 for HPA-9a, 0.025 for HPA-9b, 0.486 for HPA-15a and 0.513 for HPA-15b. Among immune thrombocytopenia individuals, no b allele of the HPA-4, -6, -7, -8 and -11 were found.ConclusionsThe results suggest HPA-1a, HPA-3b and HPA-5b are immune thrombocytopenia-specific autoepitopes.

Human platelet antigens and primary immune thrombocytopenia

“… 13 These polymorphisms have heterogeneous distribution in populations with distinct ethnic backgrounds and especially HPA-2 and HPA-5 have been described to be possible risk factors in the development of ITP. 10 , 11 , 14 , 15 In this issue, Carmo et al 16 have evaluated the association of HPAs and chronic ITP (cITP) in a small group of patients from the Amazonian region of Brazil, which has a population with a particular HPA distribution compared to the Brazilian population in general. 17 It is important to note that ITP is not a common disease and it is difficult for a single center study to enroll a large number of patients.…”

“…10 , 11 , 12 , 15 The mechanisms that explain these associations are not known yet. Although Carmo et al 16 evaluated a small group of patients from a single center, the results are interesting and further enhance the concept that ITP is a complex autoimmune disorder with mechanisms that need extensive effort to understand better and provide new and more efficient treatment possibilities.…”