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[Study of the clonal characteristics of autoantibodies in chronic idiopathic thrombocytopenic purpura].

OBJECTIVE
To define the clonality characteristics of autoantibodies in chronic idiopathic thrombocytopenic purpura (ITP).


METHODS
The heavy-chain and light-chain phenotype composition of the glycoprotein (GP)-specific IgG antibodies were analysed with a modified monoclonal antibody specific immobilization of platelet antigens (MAIPA) technique. The immunoglobulin heavy-chain gene rearrangement was analysed by PCR amplification.


RESULTS
16 out of the 43 patient sera reacted with least one of the following five GPs, namely GPIIb/IIIa, GPIb, GPIa, GPIV and GPV. Eight of 11 (73%) GP-specific antibodies displayed a restricted heavy-chain phenotypes. 80% (16/20) of the GP-specific antibodies showed a restricted kappa or lambda light-chain phenotype. Moreover, in 6 patients the GP-specific antibodies were found to be both light-chain and heavy-chain restricte. Using PCR amplification of immunoglobulin heavy-chain genes, 3 patients displayed heavy-chain genes rearrangement.


CONCLUSION
The GP-specific autoantibodies are derived from a restricted number of B-cell clones in proportion of ITP patients.