Level Of T-bet Gene Expression In Human Asthma And It's Relation With Serum IFN-γ And IL-4 Concentrations

Objective: T-bet is a recently-recognized DNA sequence, a transcription factor for IFN-y introduced firstly by Szabo SJ and colleagues in 2000.-that is transcriptively active in all IFN-y- producing cells. Asthma is a chronic obstructive disease of lower respiratory tract characterized by immunological disturbance in Th1/Th2 ratio that is dominated by Th2-type cytokines and associated tissue response. Many researches have proved the presence and role of Th2 immune reaction in asthma over the past decade. Still other experiments have indicated a weak downregulating mechanism, such as lower than normal Th1 activity, as one of the responsible factors. T-bet is being regarded as the master regulator of TM immune response as evidenced by its ability to stimulate IFN-y production, induce Th1 cell growth and differentiation, inhibit Th2-type cytokine production and reverse Th2 function to Th1 type. Higher expression of t-bet has been found in Th1-mediated pathologic disorders, similarly a lower expression in Th2-domiant features. A study has demonstrated spontaneous development of asthmatic airway changes similar to human asthma in mice with targeted deletion of the t-bet gene. So far, there is no experiment about t~bet gene expressivity in human asthma. My experiment compares asthmatics and nonasthmatics in regard to the levels of t-bet gene expressivity in PBMC. It also looks into the relationship of t-bet activity with serum concentrations of Th1-type cytokine (IFN-y) and Th2-type cytokine (IL-4).Materials and methods: 20 asthmatics and 20 nonasthmatic control subjects were chosen randomly. 5ml peripheral venous blood was collected from each subject. 4 ml blood was used to obtain PBMC on which competitive quantitative rt-PCR for t-bet mRNA was performed with beta-actin as internal standard. 1 ml blood was used to obtain serum on which ELISA was performed to measure concentrations of IFN-y and IL-4.Results: Positive t-bet expression were 12/20 (60%) in asthmatics as compared to 15/20 (75%) in nonasthmatics. Intensity of t-bet expression was (0.19+0.036) in asthma patients compared to (0.24?.026) in normal controls. T-bet expressivity was significantly lower in asthma. Serum concentrations of IFN-y and IL-4 were (1497.47?8.75)pg/mL and (15.01?.559)pg/mL in asthma group and (1690.16?7.73)pg/mL and (13.00?.564)pg/mL in the control group, respectively. IL-4 level was higher and IFN-y level was lower in asthma subjects as compare to the controls. Level of t-bet expression was positively correlated to the serum concentration of IFN-y and negatively to IL-4 in both groups.Discussion: Level of t-bet expression is reduced in asthma. Serum concentration of IFN-y is directly correlated with t-bet activity. IFN-y is a marker cytokine of Th1 cell. Hence a reduced Th1 response, determined by a reduced expression of t-bet, that is unable to downregulate Th2 response is indicated in the pathogenesis of asthma. In addition, the fact that it is able to inhibit Th2 profile independently of IFN-y indicates a moreindependent role of t-bet. Importance of t-bet in immune regulation signifies its potential role in asthma therapy in the future.