OBJECTIVETo analyze the polymorphisms of B cell activating factor (BAFF) gene and the plasma levels of BAFF in patients with idiopathic thrombocytopenic purpura (ITP), and to investigate their roles in the pathogenesis of ITP.

METHODSAlleles specific polymerase chain reaction (AS-PCR) and agarose gel electrophoresis were used to identify polymorphisms -871C/T of BAFF promotor in 133 ITP patients and 117 healthy controls. The plasma levels of BAFF were assayed by ELISA.

RESULTSIn ITP group, the frequency of C/C, C/T and T/T was 33.1%, 42.1% and 24.8%, respectively, the corresponding frequency in control group was 55.6%, 33.3% and 11.1%, respectively. The allele frequency of T in ITP and control groups was 45.9% and 27.4%, respectively. There was a significant difference in the BAFF -871C/T genotypic frequency between the ITP and control groups (P < 0.05). BAFF antigen in untreated ITP, treated patients and controls was 875.86 pg/ml, 502.59 pg/ml and 736.88 pg/ml, respectively, being also a significant difference among the three groups (P < 0.05). BAFF antigen in homozygous T/T was higher than that in homozygous C/C and heterozygous C/T, but the difference was not statistically significant (P > 0.05).

CONCLUSIONSOver expression of BAFF may be a risk factor for ITP patients. There is a correlation of the BAFF promotor polymorphism -871C/T with ITP, but the polymorphism does not affect the expression of BAFF.