Objective:To investigate the effects of Chlamydia muridarum ( Cm) respiratory tract infection on the infiltration and polarization of alveolar macrophages (AMs) and pulmonary interstitial macrophages (IMs). Methods:A C57BL/6 mouse model of Cm respiratory tract infection was established through nasal inhalation. Flow cytometry was used to detect AMs (CD45 + F4/80 + CD11c + ) and IMs (CD45 + F4/80 + CD11c -) in lung tissues at 0, 3, 7 and 14 d after Cm respiratory tract infection. The proportions of M1 (CD80 + , CD86 + , MHCⅡ + , iNOS + ) and M2 (CD206 + , Arg1 + ) macrophages in AMs and IMs were also detected. Results:(1) Cm respiratory tract infection induced the infiltration of AMs and IMs. Compared with the uninfected group (0 d), the proportions and the numbers of AMs and IMs of were significantly increased 3 d after infection ( P<0.05, P<0.01). The numbers of AMs and IMs reached the peak 7 d after infection ( P<0.001). (2) Compared with the uninfected group, the proportions of CD80 + and CD86 + cells in AMs were significantly up-regulated 3 d after infection ( P<0.05, P<0.01); the proportion of MHCⅡ + cells in AMs increased after infection and reached the peak at 14 d ( P<0.05), while the proportion of CD206 + cells decreased after infection ( P<0.05). (3) Compared with the uninfected group, the proportions of CD80 + and CD86 + cells in IMs were increased 3 d after infection ( P<0.05, P<0.001) and the proportion of MHCⅡ + cells was significantly increased 14 d after infection ( P<0.01), while there was no significant change in the proportion of CD206 + cells. (4) In AMs, the proportion of iNOS + cells increased continuously after infection ( P<0.01), while the proportion of Arg1 + cells decreased continuously after infection, especially at 7 d and 14 d ( P<0.05). In IMs, the proportion of iNOS + cells reached the peak at 7 d ( P<0.001), but the proportion of Arg1 + cells showed no significant change after infection. Conclusions:Cm respiratory tract infection induced the infiltration of AMs and IMs, stimulated the polarization of AMs and IMs towards the M1 phenotype and weakened the polarization of AMs to M2 macrophages, but had no significant influence on the polarization of IMs towards the M2 phenotype.

Objective:To investigate the role of dendritic cells (DC) in Chlamydia muridarum ( Cm) respiratory infection and their effect on adaptive immune response. Methods:C57BL/6 mice were exposed to 1×10 3 inclusion-forming units (IFU) of Cm through inhalation to establish the mouse model of Cm respiratory infection. The proportion of CD11c + MHCⅡ + DC and the expression of costimulatory molecules (CD40, CD80 and CD86) in spleen tissues were detected by flow cytometry on 0, 3 and 7 d after infection. The expression of IL-12p40, IL-10 and IL-6 at mRNA level in spleen tissues was detected by qPCR. Mouse splenic DC isolated on 7 d after Cm infection were sorted by magnetic beads and then transferred to recipient mice. Th1 response in the recipient mice was measured using intracellular cytokine staining 14 d after infection. Results:Cm respiratory infection induced massive infiltration of DC and promoted the expression of costimulatory molecules on splenic DC. The expression of IL-12 and IL-10 at mRNA level in splenic DC reached the peak on 3 d after infection. Transferring the splenic DC of Cm-infected mice into the recipient mice could alleviate the disease condition in the recipient mice after Cm infection with reduced Cm inclusion-forming units in lung tissues and significantly increased proportion of Th1 cells in lung and spleen tissues. Conclusions:Cm respiratory infection could induce the maturation and activation of DC, which promoted Th1 immune response. DC played an important role in Cm infection.

Objective:To investigate the infiltration and polarization of macrophages in mice during Chlamydia muridarum ( Cm) respiratory infection. Methods:C57BL/6 mice were intranasally infected with 1×10 3 inclusion-forming units (IFU) of Cm to establish the mouse model of Cm respiratory tract infection. The percentages of CD45 + F4/80 + cells and the macrophages expressing CD86, major histocompatibility complex Ⅱ (MHC), inducible nitric oxide synthase (iNOS) and CD206 were detected by flow cytometry. Expression of iNOS, CD206 and CCL2 at mRNA level was detected by real-time quantitative PCR. Results:Cm respiratory tract infection induced the increase of macrophages in mouse lung tissues. Compared with uninfected group, CD45 + F4/80 + macrophages were increased significantly from day 3 and reached the peak on day 7 after Cm infection. Moreover, the expression of CD86, MHCⅡ and CCL2 was increased, and the macrophages were polarized to M1 phenotype. However, the expression of M2 macrophage marker CD206 was decreased gradually. Further studies showed that iNOS expression, the indicator of M1 macrophage activation, was increased after Cm infection and reached to the top on day 7. Conclusions:Cm respiratory infection could induce the infiltration of macrophages in lung tissues and promote the polarization of macrophages to M1 phenotype.