Unappreciated HLA antibodies in adult immune thrombocytopenic purpura.
OBJECTIVE
Immune thrombocytopenic purpura (ITP) is an autoimmune disease. Platelet refractoriness is frequently seen in patients with ITP. Platelets express platelet-specific antigens and human leukocyte antigens (HLA). Platelet antibodies to platelet-specific antigens and HLA may be present, but HLA antibodies in patients with ITP have rarely been reported.


METHODS
Sera from 44 adult patients with ITP were screened for platelet antibodies by two flow cytometric assays. In method I, platelets from normal donor platelets were used as target cells to screen both platelet-specific antibodies and HLA class I antibodies. In method II, the FlowPRA Class I Screening Test kit was used to screen HLA class I antibodies. Fluorescein isothiocyanate (FITC)-conjugated sheep anti-human IgG Fc was used as the staining reagent in both methods. The negative serum control was from one of the normal males with AB blood group who had never received a transfusion. Sera from a pool of five highly sensitized patients were used as the positive control.


RESULTS
Of the 44 sera from patients with ITP, 31 (70.5%) were method I positive, and 28 (63.6%) were method II positive. There was no significant difference between the results of method I and method II (p = 0.439). The distribution of the results of these two tests was: both tests positive in 22 sera, method I positive and method II negative in nine sera, method I negative and method II positive in six sera, and both tests negative in seven sera. The mean platelet counts of patients with positive (41.0 +/- 40.0 x 10(9)/L) and negative (40.4 +/- 26.8 x 10(9)/L) tests by method I did not differ significantly (p = 0.643). The mean platelet counts of patients with (36.7 +/- 31.5 x 10(9)/L) and without (48.1 +/- 43.6 x 10(9)/L) HLA class I antibodies did not differ significantly (p = 0.59).


CONCLUSIONS
HLA class I antibodies are frequently found in ITP. The screening of platelet antibodies including platelet-specific antibodies and unappreciated HLA class I antibodies is warranted in patients with ITP.
Lin
Jeong-Shi
JS
Division of Transfusion Medicine, Department of Medicine, Taipei Veterans General Hospital, National Yang-Ming University College of Medicine, Taipei, Taiwan. jslin@vghtpe.gov.tw
Lyou
Jau-Yi
JY
Chen
Ying-Ju
YJ
Chen
Pei-Shan
PS
Liu
Hsueng-Mei
HM
Ho
Chao-Hung
CH
Hao
Tsung-Chi
TC
Tzeng
Cheng-Hwai
CH
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000906:Antibodies / Q000032:analysis; D001792:Blood Platelets / Q000276:immunology; D005434:Flow Cytometry / Q000379:methods; D006680:HLA Antigens / Q000276:immunology*; D006801:Humans; D008875:Middle Aged; D010976:Platelet Count; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000276:immunology*
D000906:Antibodies; D006680:HLA Antigens