OBJECTIVETo investigate the expression of Toll-like receptors (TLRs) in thymus of myasthenia gravis (MG) patients and the relationship with clinical features.

METHODSThymic specimens of 36 patients received extended thymectomy for MG were divided into three groups by pathological type: 13 thymoma tissues (thymoma group) and 13 thymic tissues adjacent to thymomas (parathymoma group) from 13 cases of MG patients with thymomas, and 23 thymic tissues from MG patients without thymomas (MG nonthymoma group). Twenty-one normal thymic specimens from cardiac surgery were used as controls. The levels of TLR2-4 mRNA were examined by RT-PCR, then the levels of TLR4 mRNA were assayed by real time RT-PCR and their relationship with clinical features were analyzed.

RESULTSThe levels of TLR4 mRNA among the different groups had significant differences, while there was no difference in TLR2 and TLR3 levels. The real time RT-PCR showed that the level of TLR4 mRNA in nonthymoma group was significantly higher than that in control group(0.8544+/- 0.1200 vs 0.6851+/- 0.1524, P=0.018). And so is parathymoma group compared with the thymoma group (0.8214+/- 0.1019 vs 0.7101+/- 0.0916, P=0.005). No significant difference of TLR4 mRNA level was found between the parathymoma and nonthymoma groups. Nevertheless, the expression of TLR4 in both groups was increased compared with control group. The levels of TLR4 mRNA had positive correlation with Osserman type(R=0.609; P=0.004) .

CONCLUSIONTLR4 may play a key role in the pathogenesis of MG. It was the thymic tissues adjacent to thymomas but not thymomas themselves participated in the onset of MG.