Abnormal Activation Of T Cell And The Imbalances Of Th1/Th2,Tc1/Tc2 Lymphocyte Subsets In The Pathogenesis Of Asthma

Immunological disturbances play an important role in the pathogenesis of bronchial asthma. T cell is one of the most important cells in the immune response. In addition to the expression of antigen on its surface, activated T cell releases various kinds of active substances, including cytokines, to regulate series of immunological responses. The functions of some cytokines are counter inhibitory, such as IFN- Y and IL-4. They are produced from different subsets of T lymphocytes. The imbalance between T lymphocyte subsets leads to the unusual production of cytokines, predispose to the development of the disease. Objective: To study the role of abnormal activation of T cell and the imbalance of T lymphocyte subsets in the pathogenesis of bronchial asthma. Methods: Peripheral blood samples were taken from 20 asthmatic patients during the acute attack period and during the stable period. After intracellular cytokine staining, the expression of IFN- Y /CD4(Thl)> IL-4/CD4(Th2), IFN-Y/CD8(Tcl), IL-4/CD8(Tc2) and CD226/CD3, CD226/CD4, CD226/CD8 were detected using flow cytometry. Total IgE and IL-5 were tested by ELISA; FEV1, FEVi%pre were measured using body plethysmography. Analyses were performed between groups using the analysis of variance(ANOVA); correlations between variables were analysed using Spearman's nonparametric test. Results: With theadding of PHA, the expression of CD226 on T cell subsets of asthmatic patients were higher than that of normal control(P<0.05). In asthmatic patients, the expression of CD226 during acute attack were higher than that during stable period(P<0.05). Without PHA, CD226 expressions on CD3+, CD4+, CD8+ T cells were also higher in patients with acute asthma than that of normal control(P<0.01)and the expressions of CD3+, CD8+ cells were higher in acute period than in stable period(P<0.01). The ratios of Th1/Th2N Tc1/Tc2 were significantly lower in patients with acute asthma, in comparison with those with stable asthma as well as with those of normal controls. The ratio of Th1/Th2 of stable asthmatics was lower than that of controls, whereas the difference in the ratio of Tcl/Tc2 between stable asthmatics and normal subjects was not significant (P> 0.05). The ratio of Thl/Th2 in patients with asthma, both in acute and stable state, had a significant positive correlation with FEVi. The correlation of Th2 cells and EOS in asthmatic patients were also significant. Conclusions: Abnormal activation of T cells are involved in the cascade of events leading to asthma. The expressions of CD226 on T lymphocyte subsets are higher in both acute and stable asthmatics, as compared with those of normal controls. The differences in CD226 expression between acute and stable asthmatics are also significant. Moreover, T cells are more easily activated by PHA stimulation in asthmatics than in controls. There are imbalances inTh1/Th2 and Tc1/Tc2 in patients with bronchial asthma, with thesubsets of Th playing an important role. The degree of Th1/Th2imbalance has a positive correlation with the severity of lung functionimpairment.