Maternal immunization to Gov system alloantigens on human platelets.
BACKGROUND
Immunization to platelet alloantigens can occur during pregnancy or after the transfusion of blood components. Platelet alloantibodies can cause neonatal alloimmune thrombocytopenia and posttransfusion purpura. Transfusion-induced alloimmunization to a novel platelet alloantigen system, Gov, expressed on the 175-kDa glycosyl phosphatidylinositol-anchored platelet glycoprotein, CD109, was previously described. This report describes three unrelated patients who were alloimmunized to Gov(a) or Gov(b) during pregnancy.


METHODS
Platelets were typed by using radioimmunoprecipitation for HPA-1a, -3a, -5a, -5b, Gov(a), and Gov(b) and by polymerase chain reaction-restriction fragment length polymorphism for HPA-1a, -1b, -3a, and -3b. Maternal sera were screened for platelet antibodies by using radioimmunoprecipitation and the antigen capture assay.


RESULTS
Patients 1 and 2 were investigated after the diagnosis of neonatal alloimmune thrombocytopenia in their children, and alloantibodies specific for Gov(b) and Gov(a), respectively, were detected in maternal serum. Serum from patient 3, who had mild idiopathic thrombocytopenia purpura with no detectable autoantibody, was found to contain alloantibodies to Gov(b) and to HPA-5b, presumably as a result of immunization during pregnancy. Platelet typings confirmed that the patients were at risk for alloimmunization to the respective antigen.


CONCLUSIONS
This report of three cases of maternal alloimmunization to antigens in the Gov system indicates that immunization can occur via placental transfer of antigen and that Gov system alloantibodies may be associated with neonatal alloimmune thrombocytopenia.
Bordin
J O
JO
Department of Hematology and Transfusion Medicine, Universidade Federal de São Paulo, Escola Paulista de Medicina, Brazil.
Kelton
J G
JG
Warner
M N
MN
Smith
J W
JW
Denomme
G A
GA
Warkentin
T E
TE
McGrath
K
K
Minchinton
R
R
Hayward
C P
CP
D000328:Adult; D000911:Antibodies, Monoclonal / Q000276:immunology; D000937:Antigen-Antibody Reactions; D016824:Antigens, Human Platelet / Q000276:immunology*; D001789:Blood Group Antigens / Q000276:immunology; D001787:Blood Group Incompatibility / Q000209:etiology; D001788:Blood Grouping and Crossmatching; D000939:Epitopes; D005260:Female; D005331:Fetomaternal Transfusion; D006684:HLA-DR Antigens / Q000032:analysis; D006801:Humans; D007114:Immunization; D007518:Isoantibodies / Q000032:analysis; D007519:Isoantigens / Q000276:immunology*; D017713:Platelet Transfusion / Q000009:adverse effects; D011247:Pregnancy
D000911:Antibodies, Monoclonal; D016824:Antigens, Human Platelet; D001789:Blood Group Antigens; D000939:Epitopes; D006684:HLA-DR Antigens; D007518:Isoantibodies; D007519:Isoantigens