Influence OfIL-21/IL-21R Signaling Pathway On The Inflammato Ry Response To Chlamydia Trachomatis Airway Infection

Objective and content:IL-21/IL21 R signaling pathway expressed in a variety of immune cells can improve the immunocytes antigenic specificity response to anti-tumor,anti-infection and autoimmune diseases,which promotes the transition between innate and adaptive immunity.The current study reported that IL-21/IL-21 R signaling pathway promotes inflammatory cells,such as granulocytes,lymphocytes,plasma cells and others recruited to the site of infection,and then regulates immune response.C hlamydia muridarum is an intracellular bacterium and has specific development cycle,which induces host lung inflammatory through the airway infection.Because of the limited understanding of the pathogenicity mechanism of pathogen and the mechanism of host defense,there is no effective vaccine for t he prevention and treatment of chlamydia disease.To investigate the effects of IL-21/IL-21 R signaling pathway on the inflammotory response of C m airway infection,we firstly definited whether C m infection promotes the production of IL-21 mRNA or not,and then explored the pneumonia histopathologic and the change of mononuclear cell infiltration in IL-21R-/-mice.We further examined the effects of IL-21/Il-21 R signaling pathway on infiltration of CD4~+T、CD8~+T、γδT、NK、PMN cells and expression of MIP-2、KC、CXCR2、IL-6、TNF-α、IL-1β in lung following Cm airway infection to define the role of IL-21/Il-21 R signaling pathway in chlamydia pneumonia of mice.These studies will provide theoretical basis for the immunological mechanism of intracellular bacterial infection.Methods:Chlamydial pneumonia was induced in WT mice by intranasal inoculation of Cm.The mice were killed at different time points after 14 days of infection.To definite the production of IL-21 mRNA induced by C m,we used RT-PCR to detect the expression of IL-21 R mRN A in lung tissues of mice.WT mice and IL-21R-/-mice were intranasally infection with the same dose of C m,then the lung tissues of mice at different time points of infection were made into the mononuclear cell suspensation.Brilliant blue staing counts the mononuclear cells of lung tissues.The lung tissues of WT mice and IL-21R-/-mice were used to observe the pathological changes by paraffin section and HE staing.To detect the infiltration of CD3~+CD4~+T、CD3~+CD8~+T、CD3~+γδ~+T、CD3-NK1.1~+NK、CD11b~+Gr1~+PMN cells in lung tissues,lung mononuclear cells were prepared and stained with anti-CD3,anti-CD4,anti-CD8,anti-γδ,anti-NK1.1,anti-CD11 b,anti-Gr1 fluorescent antibody with flow cytometry.The C hemokines of MIP-2、KC、CXCR2 mRNA and inflammatory factors of IL-6、TNF-α、IL-1β mRNA expression in lung were measured by using RT-PCR.Results:The expression of IL-21 mRNA in chlamydia pneumoniae induced by ariway infection in C hlamydia trachomatis mice pneumoniae(C m)increased on the 3 rd day and reached the highest level on the 7th day(P﹤0.001),then gradually decreased on the 14 th day compared with WT mice.The total number of mononuclear cells in the lungs of WT mice and IL-21R-/-mice was significantly increased with time extending of infection and reached the peak level on the 14 th day.Compareed with WT mice,the total number of mononuclear cells in lung tissues was decreased in IL-21R-/-mice on the 3rd,7th,14 th day,but there was no significant difference between the two groups of mice.HE staing of lung tissues showed that the inflammatory response was lighter after knock out IL-21 R on the 3rd and 7th day following C m infection,but on the 14 th day was still more serious than WT mice.To investigate the effects of IL-21 on infiltration C D4~+T、CD8~+T、γδT、NK and PMN cells in lung following C m airway infection of WT amd IL-21R-/-mice,lung mononuclear cells of different time of infection were stained with fluorescent antibody.Compared with WT mice,it showed that the percentages and total number of CD4~+T significantly increased,but C D8~+T,NK,PMN cells significantly decreased on the 7th day(P<0.05,P<0.01,P<0.001)in the lung of IL-21R-/-mice.The percentages and total number of γδT had no significant differences at different time of infectio n after knocking out IL-21 R.The expression of MIP-2、IL-1β、TNF-α、IL-6、CXCR2 mRNA in lung tissues of IL-21R-/-mice on the 7th day were significantly decreased(P<0.05,P<0.01,P<0.001),but the expression of MIP-2、IL-1β、TNF-α、IL-6、KC mRNA in lung tissues of IL-21R-/-mice on the 14 th day were significantly increased(P﹤0.01,P﹤0.001)compared with WT mice.Conclusions:1.Cm airway infection induces IL-21 mRNA expression in the lung of mice.2.IL-21/IL-21 R signaling pathway significantly promotes infiltration of C D8~+T and NK cells into lung tissues while inhibits infiltration of C D4~+T cells into lung tissues and has no effect on the proliferation of γδT cells in lung following C m airway infection.3.IL-21/IL-21 R signaling pathway may promote recruitment of neutrophils to lung tissues by inducing the expression of chemokines and inflammatory factors response to C m airway infection,and it is closely related that the inflammatory of lung tissues recovers slowly with high expression of chemokines and inflammatory factors...