OBJECTIVE: To identify the T helper cell predominant differentiation in asthmatic patients and to explore the modulation of T cell-specific transcription factors T-bet/GATA-3. METHODS: Thirty-two asthmatic patients were enrolled, among whom 18 were atopic defined by positive antigen skin test and 12 were children. Lymphocytes were isolated from peripheral blood and incubated with PHA (100 microg/ml) at 37 degrees C for 48 hours. INF-gamma and IL-4 concentrations in the supernatant were detected by ELISA. The T-bet and GATA-3 mRNA expression levels in lymphocytes were assayed by reverse transcription-polymerase chain reaction (RT-PCR) while the ratio of CCR3+ and CCR5+ cells in lymphocytes was counted by flow cytometry (FCM) after direct immunofluorescence staining. RESULTS: IL-4 concentration in the lymphocyte supernatant of the asthmatic group was (118 +/- 25) microg/L, which was significantly elevated compared to that of the healthy control group (75 +/- 12) microg/L (P < 0.01). When subgroups of asthmatic patients were compared, the results showed that atopic subjects had a higher IL-4 level than non-atopic subjects [(126 +/- 23) microg/L vs (107 +/- 26) microg/L, P < 0.01], but no significant difference was demonstrated between adults and children [(118 +/- 25) micro g/L vs (121 +/- 25) microg/L, P > 0.05]. Significantly lower concentration of INF-gamma in the asthmatic group was detected as compared to the control [(651 +/- 85) microg/L vs (1 179 +/- 332) microg/L, P < 0.001]. The concentration of INF-gamma was higher in atopic subjects than in non-atopic subjects [(618 +/- 89) micro g/L vs (680 +/- 83) microg/L, P < 0.01], but no difference was found between adults and children. The percentage of CCR3+ cells in lymphocytes was (9.4 +/- 5.8)% in the asthmatic group and (4.9 +/- 2.3)% in the control (P < 0.05), while the percentages of CCR5+ cells was (6 +/- 7)% and (13 +/- 7)%, respectively (P < 0.05). RT-PCR revealed that T-bet mRNA expression levels were as follows: 0.13 +/- 0.03 in the asthmatic group and 0.18 +/- 0.04 in the control (P < 0.01); 0.120 +/- 0.030 in atopic subjects and 0.140 +/- 0.010 in the non-atopic subjects (P < 0.05); 0.120 +/- 0.020 in children and 0.130 +/- 0.020 in adults (P > 0.05). The levels of GATA-3 mRNA expression were 0.43 +/- 0.07 in asthma and 0.29 +/- 0.09 in the control (P < 0.01), however, no differences were found between atopic and non-atopic, children and adults (0.50 +/- 0.12 vs 0.40 +/- 0.10, 0.44 +/- 0.09 vs 0.43 +/- 0.07, respectively, P > 0.05). A positive correlation was found between concentration of INF-gamma and T-bet mRNA level (r=0.663, P < 0.01), while no correlation with GATA-3 mRNA expression was found. The concentration of IL-4 was negatively correlated with T-bet mRNA level (r=-0.250, P < 0.05) and positively with GATA-3 mRNA level (r=0.72, P < 0.01). It was interesting that a closer relationship existed between the ratio of T-bet to GATA-3 and the ratio of INF-gamma to IL-4 (r=0.873, P < 0.01). CONCLUSIONS: In asthma there is a tendency of Th2 polarization with over-production of Th2-like cytokines in which T-bet deficiency may be a key factor. T-bet might direct T cells to Th1 differentiation while GATA-3 orientated Th2 maturation. Considering the fact that committed Th2 cells underwent re-differentiation induced by T-bet, this novel Th1-specific transcription factor is a fascinating target gene for modifying to restore the Th1 and Th2 balance.