Maternal alloimmunization against fetal platelet antigens: a prospective study

Abstract

Neonatal alloimmune thrombocytopenia (NAIT) is induced by maternal alloantibodies to fetal platelet antigens. This prospective study was carried out to evaluate the incidence of anti-platelet antibodies in 933 mother-child pairs where the mother and child were typed for the human platelet antigens (HPA)-1, -2, -3, -5. Sera from mismatched mother-child pairs were screened for anti-platelet antibodies, anti-HLA class I and blood group ABO IgG antibodies. Platelet-specific antibodies were anti-HPA-3a in one and anti-HPA-5b in 17 neonates, respectively. All these neonates had normal platelet counts. One woman had autoreactive antibodies. Anti-HLA class I and anti-blood group A IgG antibodies were detected in five and four neonates, respectively, born with a platelet count < 150 x 10(9)/l. None of the 11 homozygous HPA-1b mothers became immunized against their heterozygous offspring. The maternal HLA-allotypes HLA-DR52 and -DR6, typically found in individuals immunized against HPA-1a and -5b, respectively, were found in three of 11 HPA-b/b nonresponders and eight of the anti-HPA-5b responders. The results indicate that a risk for NAIT due to HPA-2 and -3 alloimmunization is low. The HLA allotypes do not predict the risk for NAIT due to HPA-1 or -5 alloimmunization. Maternal anti-HPA-5b antibodies do not correlate with the platelet count in the neonate.

Incidence and Consequences of Neonatal Alloimmune Thrombocytopenia: A Systematic Review

“…2 Panzer et al stated that they only included deliveries with an uncomplicated history of pregnancy and delivery. 9 This suggests that premature deliveries were excluded. In the other 2 studies, premature deliveries were not excluded, without specific numbers given 1,8 …”

“…Only in the studies by Panzer et al 9 and Saino et al 10 was parity of the mothers mentioned. In the study of Panzer et al, only the parity of the HPA-1a negative mothers (n = 11) was mentioned: 10 were primiparae, 2 had previous abortions, and 1 had a third delivery with 4 previous abortions.…”

“…In the studies of Uhrynowska et al and Panzer et al, HPA typing was done in all maternal plasma, followed by evaluation for HPA-1a antibodies in case of HPA-1a incompatibility. 9,11 In the other studies, this was only done in case of confirmed neonatal thrombocytopenia. 1,2,8,9 In the study of Burrows et al, the percentage of alloimmunization (formation of anti HPA-1a antibodies) in case of /L HPA-1a incompatibility, no anti HPA-1a antibodies detected.…”

“…1 Panzer et al included only those deliveries with an uncomplicated history of pregnancy and delivery, without further specification. 9 Only Burrows et al provided information about the history of the mothers with affected offspring. 8 In their study of 18 mothers found to have HPA-1a alloimmunization, 15 had a previous affected child, and 3 allo-immunized women were sisters of women with known NAIT.…”

“…After critical appraisal of the full text of the remaining 21 articles independently by 2 authors (MK and NP), 6 studies were included in the review. 1,2,[8][9][10][11] The main reason for exclusion was that screening was not performed in a low-risk population but in newborns selected by the history of siblings who suffered from fetal and neonatal alloimmune thrombocytopenia (FNAIT) during pregnancy or at birth. Another important reason for exclusion was the use of case finding through maternal HPA-1a typing in unselected pregnant women, with further analysis in those women who were typed negative for HPA-1a.…”