¡¾Abstract¡¿ AIM: To evaluate the effect of antiª²CD8 monoclonal antibody (antiª²CD8mAb) on airway inflammation of Balb/c mice with respiratory syncytial virus(RSV)ª²induced asthma. METHODS: Fifty mice were randomly divided into 5 groups (n=10 each group): PBS control group, OVA group, OVA/RSV group, antiª²CD8mAb treated group and IgG2¦ÁmAb treated control group. Lung histopathological changes were evaluated by HE stain. Airway responsiveness was assessed using a whole body plethysmography. Cells in bronchoalveolar lavage fluid(BALF) were counted and classified and the supernatants of the BALF were used for detection of interleukin(IL)ª²4, ILª²5 and interferon(IFN)ª²¦Ã. The percentage of CD4+(IFNª²¦Ã+, ILª²4+, ILª²5+), CD8+(IFNª²¦Ã+, ILª²4+, ILª²5+)T lymphocytes and the ratio of Th2/Th1, Tc2/Tc1 in peribronchial lymph nodes(PBLN) were analysed by threeª²color flow cytometry method. RESULTS: Intraperitoneal administration of antiª²CD8mAb can remarkably inhibit airway inflammation and airway hyperresponsiveness(AHR). Eosinophils and IFNª²¦Ã, ILª²4, ILª²5 levels in BALF decreased in antiª²CD8mAb therapeutic group compared with OVA/RSV group(P<0.01, respectively). The percentage of CD8+(IFNª²¦Ã+, ILª²4+, ILª²5+)T lymphocytes and the ratio of Tc2/Tc1 decreased in antiª²CD8mAb therapeutic group compared with OVA/RSV group(P<0.01, respectively). A close correlation between the percentage of CD8+(IFNª²¦Ã+, ILª²4+, ILª²5+)T lymphocytes and IFNª²¦Ã, ILª²4, ILª²5 levels in BALF from OVA/RSV group, antiª²CD8mAb therapeutic group was demonstrated (rs=0.765, P<0.01; rs=0.825, P<0.01; rs=0.893, P<0.01). CONCLUSION: Antiª²CD8mAb might suppress airway inflammation and AHR through the mechanism that CD8+T lymphocytes transfer from Tc1 to Tc2, which may be relative to the increase of ILª²4, ILª²5, the gathering of inflammatory cells in the airway and AHR. ......