Platelet‐specific alloantigens and antibodies in Tunisian women after three or more pregnancies

Abstract

Pregnancy may allow alloimmunization against human platelet antigens (HPA), which can lead to neonatal alloimmune thrombocytopenia (NAIT). The specificities of alloantibodies are closely related to the distribution of the HPA systems. A total of 281 Tunisian multiparous women (mean number of pregnancies: 4.5) were phenotyped for the HPA-1, -3 and -5 systems, by monoclonal antibody immobilization of platelet antigens (MAIPA). We searched for antibodies against HPA-1a, HPA-3a, HPA-5b and HPA-5a in HPA-1b1b, HPA-3b3b, HPA-5a5a and HPA-5b5b individuals, respectively. The gene frequencies were: 0.83 for HPA-1a, 0.17 for HPA-1b, 0.78 for HPA-3a, 0.22 for HPA-3b, 0.82 for HPA-5a and 0.18 for HPA-5b. Anti-HPA-5b antibodies were present in eight sera and anti-HPA-3a antibodies were present in one serum. The anti-HPA-5b system is the most frequently involved in platelet alloimmunization in Tunisian multiparous women. However, prospective trials are required to confirm this result and to determine the exact frequencies and clinical relevance of platelet alloantibodies in pregnant Tunisian women.

Gene frequencies of the HPA-1 to -6 and -15 human platelet antigens in Tunisian blood donors

“…The distribution of HPA‐1, HPA‐3, and HPA‐5 systems confirms previous Tunisian studies (5–6) and it is similar to that reported in other Maghrebian populations (Moroccan Berbers and Algerian) (11–12). Tunisians have the highest frequency for the HPA‐1b (0.22) and ‐5b (0.20) alleles, but the lowest one for HPA‐3b allele (0.25).…”

“…However, studies have mainly been performed in North American, European, and Oriental populations. In Tunisia, little is known about platelet immunogenetics and previous reports suggest that the frequency of platelet alloimmunization may differ with that seen in Whites and Asians (4–5). Tunisia is known to have a very heterogeneous population as a result of its history (6).…”