Neonatal alloimmune thrombocytopenia associated with maternal anti-HLA antibody: a case report.
OBJECTIVE
Although neonatal alloimmune thrombocytopenia (NAIT) due to maternal sensitization to human platelet antigens is well described, the role of maternal anti-human lymphocyte antigen (HLA) antibodies in NAIT is not yet firmly established.


METHODS
A 31-week-old girl born prematurely to a G2POA1 mother was noted to have thrombocytopenia which lasted 18 days without any evidence of infection.


METHODS
Platelet-associated IgG, anti-platelet antibody, and platelet PL(A1) antigen typing were determined using a commercial solid-phase red cell adherent test. Antibodies to platelet glycoproteins human platelet antigen (HPA) 1 to 5 were determined using a commercial ELISA. Anti-HLA antibodies were assayed using a standard lymphocytotoxicity test. Activities and IgG subclass of anti-HLA antibodies in plasma of the mother and other postpartum mothers were measured using purified HLA antigens in an enzyme linked immunoassay.


RESULTS
Both mother and infant were positive for HPA-1 (PL(A1)) antigens. The mother's HLA phenotype was A3, A31, B7, B27. The level of platelet-associated IgG was not increased on maternal platelets; however, increased platelet-associated IgG was detected on the infant's platelets. Antibodies to platelet glycoproteins HPA1 to 5 were not detectable in the maternal plasma. Maternal serum was positive for anti-HLA antibodies, which reacted to 23 of 27 panel cells. The presence of HLA antibodies was confirmed by enzyme-linked immunoassay. Of note, the maternal antibodies reacted positively to the infant's platelets and anti-IgG anti-HLA antibodies were detected in the serum sample from the infant collected at birth. When the activity and IgG subclass of the maternal anti-HLA antibodies were compared with those of other mothers known to have high anti-HLA antibody activity, no differences were noted.


CONCLUSIONS
This report documents a patient with neonatal thrombocytopenia induced by maternal IgG anti-HLA antibody. Neither activity nor IgG subclass could explain the occurrence of NAIT. The factors that contribute to NAIT induced by maternal anti-HLA antibodies remain to be identified.
del Rosario
M L
ML
Department of Pathology, University of Florida Health Science Center, Gainesville, USA.
Fox
E R
ER
Kickler
T S
TS
Kao
K J
KJ
D000328:Adult; D016824:Antigens, Human Platelet / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005331:Fetomaternal Transfusion / Q000276:immunology*; D006680:HLA Antigens / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000276:immunology*; D010976:Platelet Count; D011247:Pregnancy; D013921:Thrombocytopenia / Q000276:immunology*
D016824:Antigens, Human Platelet; D006680:HLA Antigens; D007074:Immunoglobulin G