Abstract： Objective To explore the relationship between the dendritic cell (DC) subsets and abnormal expression of transcription factors Gata-3 and T-bet in patients with immune thrombocytopenia (ITP).Methods The plasmacytoid DC (pDC) and myeloid DC (mDC) of 33 ITP (16 untreated,17 remitted) patients and 12 healthy controls were analyzed by flow cytometry(FCM).The expressions of Gata-3 mRNA and T-bet mRNA in peripheral blood mononuclear cell (PBMNC) were detected by reverse transcription-polymerase chain reaction (RT-PCR).The levels of intedeukin-4 (IL-4) and interferongamma (IFN-γ) were measured by FCM in 33 ITP patients and 12 healthy controls.Results The percentage of pDC in PBMNC was 0.49％ ±0.18％ in untreated and it was higher than that in remitted ITP patients (0.27％ ±0.17％) and in controls (0.32％ ±0.13％) (both P ＜0.05).The percentage of mDC in PBMNC was 0.23％ ±0.17％ in untreated,which was lower than that in remitted ITP patients (0.33％ ± 0.18)％ and in controls(0.31％ ±0.11％),but no statistic difference in mDC expression existed among 3 groups (P ＞0.05).pDC/mDC ratios was (3.15 ± 2.01) in untreated ITP patients and it was higher than that in remitted ITP patients (0.81 ± 0.32) and in controls (1.07 ± 0.44) (both P ＜ 0.05).The relative mRNA expression levels of Gata-3 were 2775 ± 489,1357 ± 307 and 652 ± 165 respectively.And the expression of Gata-3mRNA in untreated group was higher than that in remission group or healthy controls (both P ＜ 0.05).The relative mRNA expression levels of T-bet were 782 ± 394,583 ± 176 and 576 ± 120.No statistic difference in T-bet expression existed among 3 groups (P ＞ 0.05).Gata-3mRNA/T-bet mRNA ratio was (4.13 ± 1.69) in untreated group and it was higher than that of remission group (2.45 ±0.69) or controls (1.15 ±0.27) (both P ＜0.05).The level of IL-4 in the untreated group was 9.14％ ±4.34％and it was higher than that of remission group (4.78％ ± 1.69％) or controls (4.86％ ± 1.41％).The level of IFN-γ in the untreated group was lower than that of controls (P ＜ 0.05).Significant positive correlations existed between Gata-3 and pDC/mDC ratio (r =0.585,P ＜0.01).Significant positive correlations existed between Gata-3 and IL-4 (r =0.463,P ＜ 0.05).Conclusion The mechanism of ITP may be due to a disorder of DC subsets and a high expression of Gata-3.