Abstract: 【Abstract】Object:First,to observe the expression of TLR4 on monocytes in peripheral blood after RSV infection and the relationship between TLR4 expression and disease severity or atopic disposition;Second,,to evaluate the relationgship between IFN-γ concentration and disease severity or atopic disposition in acute infection phase.Method:group 1:test group:30 children who got pneumonia,then the group was devided into two subgroup:22 children are the mild and moderate ones,8 children are severe ones.On the basis of atopy(eczema,for example)and family history(asthma,allergic rhinitis,allergic conjunctivitis,atopic dermatitis and so on)，we devide the group into two groups:one group with atopic disposition concludes 19 children and the other without atopic disposition concludes 11 children.Group 2:27 children admitted into hospital for surgical reasons without respiratory infection in the last week.Results:1.The expression of TLR4 in the test group is 22.29±9.46%,and in control group is 12.67±9.46%,there is statistical significance(P =0.001<0.05）by U test.TLR4 in mild and moderate group of test group is 21.44±16.33%,while in severe group is 24.61±17.28%,there is no statistical significance(P =0.872>0.05）.TLR4 in test group with atopic disposition is 21.99±16.14%,and in group without atopic disposition is 22.76±17.48%,there is no statistical significance(P =0.966>0.05).2.The concentration of IFN-γ in test group is 254±504.48ng/L,and in control group is 259.89±829.91ng/L,and between the two groups there is no statistical significance(P =0.64>0.05).The concentration in mild and moderate group of test group is 324.8±568.19ng/L,while in severe grouop is 62.36±167.6ng/L,obviousely there is statistical significance(P =0.045<0.05）.The concentration in test group with atopic disposition is 350.19±586.57ng/L,and in test group without atopic disposition is 90.09±267.56ng/L,and there is no statistical significance(P =0.25>0.05）.Conclusion:The expression of TLR4 on peripheral blood monocyte up-regulates during RSV infection.But it does not obviously relate to the severity of disease,and is not influced by atopic disposition during acute RSV infection.The concentration of IFN-γ in test group is not significantly different from that of control test.It negatively relates to disease severity,that the concentration of severe children is lower than that of mild children.It is rational to use IFN-γfor severe RSV pneumonia.During RSV infection ,the concentration of IFN-γ has not distinct relation with atopic disposition.

Key words: Respiratory Syncytial Virus, Toll-like Receptor 4, IFN-γ