[Study on the relations between HLA-DRB1 alleles and idiopathic thrombocytopenic purpura in children].
OBJECTIVE
To gain an insight into the relations between human leukocyte antigen-DRB1 (HLA-DRB1) alleles and idiopathic thrombocytopenic purpura (ITP) in children.


METHODS
Polymerase chain reaction-sequence specific oligonucleotide (PCR-SSO) was used to identify DRB1 alleles of 42 children with ITP. Among them, 36 were identified for anti-GPIIb/IIIa and anti-GPIb/Ix autoantibody by modified monoclonal antibody specific immobilization of platelet antigens.


RESULTS
Compared with health controls, the frequency of HLA-DRB1*17 significantly increased (P<0.05, relative risk=2.76, etiologic factor=0.1064) and the frequency of HLA-DRB1*1202 significantly decreased (P<0.025, relative risk=0.20, prophylactic factor=0.7616) in children with ITP. In comparison with patients of good response to steroids and IVIgG therapy, the frequency of HLA  DRB1*11 significantly increased (Chi-square=6.091, P<0.025) in patients with a poor response, furthermore, the most of HLA-DRB1*11  positive patients were female teen-agers. Twenty-seven patients (75%) had anti  GPIIb/IIIa and seventeen (47.22%) had anti_GPIb/Ix autoantibodies. The positivities of both anti_GP IIb/IIIa (P=0.02) and anti-GPIb/Ix (P=0.01) were associated with HLA-D RB1*02. However, the positivity of autoantibodies between refractory and non-refractory patients showed no significant difference.


CONCLUSIONS
The allele of HLA-DRB1*17 seems to predict susceptibility of ITP in children, while HLA-DRB1*1202 appears to be protective to ITP. The allele of HLA  DRB1*11 plays an important role in resistance to steroid and IgG therapy in children with ITP. It seems that the response to the antigenic epitope of GPIIb/IIIa and GPIb/Ix is restricted by HLA-DRB1*02, while the presence of the antibodies could not predict prognosis. In conclusion, the above preliminary findings indicate that genetic factors influence the clinical course of ITP, but the exact mechanism needs to be investigated further.
Wang
Hongmei
H
Department of Paediatrics, Shandong Provincial Hospital, Jinan, Shandong, 250021 P.R.China. whtwhm@263.net
Shen
Baijun
B
Yan
Wenying
W
Hou
Ming
M
Zhu
Na
N
Qi
Hongying
H
Hou
Huaishu
H
D000293:Adolescent; D000483:Alleles; D001323:Autoantibodies / Q000097:blood; D002648:Child; D002675:Child, Preschool; D004247:DNA / Q000235:genetics; D004351:Drug Resistance / Q000235:genetics; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006684:HLA-DR Antigens / Q000235:genetics*; D059811:HLA-DRB1 Chains; D006801:Humans; D007074:Immunoglobulin G / Q000627:therapeutic use; D008297:Male; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000276:immunology; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000276:immunology; D010980:Platelet Membrane Glycoproteins; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000097:blood / Q000188:drug therapy / Q000235:genetics*; D013256:Steroids / Q000627:therapeutic use
D001323:Autoantibodies; D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains; C553514:HLA-DRB1*12:02 antigen; D007074:Immunoglobulin G; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D019038:Platelet Glycoprotein GPIb-IX Complex; D010980:Platelet Membrane Glycoproteins; D013256:Steroids; C032193:glycoprotein receptor GPIb-IX; D004247:DNA