Background: In the past few years,Mycoplasma pneumoniae(Shi et al. Lancet 390:946–958, 2017) infection has been reported more in China. However, there are few studies on the clinical characteristics and prognosis of necrotizing pneumonia (NP) (Griffiths et al. Nature 583:615–619, 2020) caused by different pathogens.Methods: A retrospective analysis was performed, including 31 children with a clinical diagnosis of NP in the hospital from January 1, 2013 to January 31, 2020. A total of 11 children with MPNP were included in the observation group and the other 20 children with other pathogens were included in the control group. The clinical manifestations, laboratory data, imaging findings, treatments and outcomes were analyzed.Results: The proportion of dyspnea cases was significantly higher in the non-Mycoplasma pneumoniaenecrotizing pneumonia (N-MPNP) group than that in theMycoplasma pneumoniaenecrotizing pneumonia (MPNP) group (P = 0.02).The LDH level of all patients in the MPNP group was higher than the normal value, with a median value of 805.0 U/L, which was significantly higher than those in the N-MPNP group (414.0 [299.9–540.6] U/L;Z = − 2.518;P = 0.012). The white blood cells (WBCs) count of the N-MPNP group was 17.8 (11.1–21.7) × 10⁹/L, which was significantly higher than that of the MPNP group (10.2 [6.3–14.1] × 10⁹/L;P < 0.05). The mean time of pulmonary necrosis in the MPNP group was 20.9 ± 6.9 days, which was higher than that of the N-MPNP group (16.8 ± 6.1 days;t = 3.101;P = 0.004). The incidence of pleural effusion in the N-MPNP group (19 patients, 95%) was significantly higher than that in the MPNP group (six patients, 54.55%) (P = 0.013). Among them, two patients received bronchoscopy lavage at a maximum four times, and the cases of plastic bronchitis were seen only in the MPNP group (3 cases;P = 0.037).The length of stay was 18 (10–22) days in the MPNP group and 23.5 (13.5–47) days in the N-MPNP group and no significant difference was observed between the two groups (Z = − 1.923,P = − 0.055).Conclusions: MP infection is the most common infection in children with NP in the Suzhou area. There is no gender and age difference between MPNP and N-MPNP, but the bacterial infection was mainly observed in the N-MPNP group. Children in the N-MPNP group have more severe clinical symptoms, were more prone to shortness of breath, had a longer hospital stay, and had earlier imaging manifestations of necrosis, whereas children in the MPNP group were more likely to have plastic bronchitis. The level of WBC and LDH and the nature of pleural effusion can be used to identify MPNP and N-MPNP to some extent. The prognosis of MPNP was better than that of N-MPNP. There were no death cases. Pleural thickening, pulmonary fibrosis, and bronchiectasis were the most common sequelae. Compared with N-MPNP, the recovery time of lung imaging in MPNP was shorter.

Background: Within the past 3-5 years, Mycoplasma pneumoniae has become a major pathogen of community-acquired pneumonia in children. The pathogenic mechanisms involved in M. pneumoniae infection have not been fully elucidated.Methods: Previous protein microarray studies have shown a differential expression of CXCL9 after M. pneumoniae infection. Here, we conducted a hospital-based study to explore the clinical significance of the type 1 immune response inflammatory factors interferon (IFN)-γ and CXCL9 in patients with M. pneumoniae pneumonia (MPP). Then, through in vitro experiments, we explored whether CARDS toxin stimulated F-DCs (dendritic cells incubated with Flt3L) to promote Th-cell differentiation; we also investigated the IFN-γ-induced CXCL9 secretion pathway in macrophages and the role of CXCL9 in promoting Th1 cell migration.Results: The CXCL9 expression level was upregulated among patients with a higher fever peak, fever duration of greater than 7 days, an imaging manifestation of lobar or segmental, or combined pleural effusion (P<0.05). The peripheral blood levels of IFN-γ and CXCL9, which were higher in patients than in the healthy control group, were positively correlated with each other (r=0.502, P<0.05). In patients, the CXCL9 expression level was significantly higher in the bronchoalveolar lavage fluid (BALF) than in the peripheral blood, and the BALF CXCL9 expression level was higher than that in the healthy control group (all P<0.05). Our flow cytometry analysis revealed that M1-phenotype macrophages (CD16⁺CD64⁺CD163⁻) were predominant in the BALF from children with MPP. In in vitro experiments, F-DCs stimulated with CARDS toxin promoted the differentiation of CD4⁺IFN-γ⁺ Th (Th1) cells (P<0.05). Moreover, IFN-γ induced high levels of CXCL9 expression in M1-type macrophages in a dose-dependent and time-dependent manner. Additionally, macrophages transfection with STAT1-siRNA-1 downregulated the expression of CXCL9 (P<0.05), and CXCL9 promoted Th1 cell migration (P<0.05).Conclusions: Our findings suggest that CARDS toxin induces a type 1 immune response positive feedback loop during M. pneumoniae infection; this putative mechanism may be useful in future investigations of immune intervention approaches for M. pneumoniae pneumonia.

IFN-γ–inducible protein 16 (IFI16) recognizes viral DNAs from both nucleus-replicating viruses and cytoplasm-replicating viruses. Isoform 2 of IFI16 (IFI16-iso2) with nuclear localization sequence (NLS) has been studied extensively as a well-known DNA sensor. However, the characteristics and functions of other IFI16 isoforms are almost unknown. Here, we find that IFI16-iso1, with exactly the same length as IFI16-iso2, lacks the NLS and locates in the cytoplasm. To distinguish the functions of IFI16-iso1 and IFI16-iso2, we have developed novel nuclear viral DNA mimics that can be recognized by the nuclear DNA sensors, including IFI16-iso2 and hnRNPA2B1. The hexanucleotide motif 5′-AGTGTT-3′ DNA form of the nuclear localization sequence (DNLS) effectively drives cytoplasmic viral DNA nuclear translocation. These nuclear viral DNA mimics potently induce IFN-β and antiviral IFN-stimulated genes in human A549 cells, HEK293T cells, and mouse macrophages. The subcellular location difference of IFI16 isoforms determines their differential functions in recognizing viral DNA and activating type I IFN–dependent antiviral immunity. IFI16-iso1 preferentially colocalizes with cytoplasmic HSV60mer and cytoplasm-replicating vaccinia virus (VACV), whereas IFI16-iso2 mainly colocalizes with nuclear HSV60-DNLS and nucleus-replicating HSV-1. Compared with IFI16-iso2, IFI16-iso1 induces more transcription of IFN-β and IFN-stimulated genes, as well as stronger antiviral immunity upon HSV60mer transfection or VACV infection. IFI16-iso2, with the ability of nuclear-cytoplasmic shuttling, clears both invaded HSV type 1 and VACV significantly. However, IFI16-iso2 induces more type I IFN–dependent antiviral immunity than IFI16-iso1 upon HSV60-DNLS transfection or HSV type 1 infection. Our study has developed potent agonists for nuclear DNA sensors and also has demonstrated that IFI16 isoforms with cytoplasmic and nuclear locations play differential roles in innate immunity against DNA viruses.

Mycoplasma pneumoniae caused lower respiratory tract infection in children and can exacerbate these infections through the production of various inflammatory factors, with chemokines playing a key role. However, the pathogenesis of this infection is complicated and thus has not been thoroughly studied. We clarified that cytokine expression levels were analyzed in both peripheral blood and bronchoalveolar lavage fluid (BALF), and in vitro assays were conducted using THP-1 macrophages. We discovered that, compared to control children, M. pneumoniae pneumonia (MPP) patients expressed significantly higher levels of CXCL10 both in the peripheral blood and BALF. Moreover, numbers of macrophages, predominantly with a M1 phenotype, were significantly increased in BALFs of children of MPP. In vitro, coculture with IFN-γ or activated CD4⁺ Th1 cells significantly promoted CXCL10 expressions in THP-1 derived macrophages, which was largely reversed by siRNA-mediated down regulation of STAT1. In addition, IFN-γ-stimulated macrophages greatly promoted the trans-migration of Th1 cells. our data show that Th1 cells-derived IFN-γ augments CXCL10 production in macrophages via the JAK-STAT1 pathway, which subsequently recruits more immune cells like Th1 cells into the infection sites, thereby constituting a positive feedback loop and aggravating the type I inflammatory responses in MPP patients.

The role of long non-coding RNAs (lncRNA) in asthma remains unclear. In this study, we examined the role of long non-coding RNA taurine upregulated 1 (lncRNA TUG1) in asthma. We found that lncRNA TUG1 is one of the differentially expressed lncRNAs in the monocytes of asthmatic children and is associated with Th cell differentiation. LncRNA TUG1 and miR-29c are mainly distributed in the cytoplasm of macrophages. Our data suggested that lncRNA TUG1 increased in macrophages stimulated by House Dust Mite in a dose-dependent manner. Using loss- and gain of function strategy, we found that miR-29c might regulate Th2 cell differentiation by directly targeting co-stimulatory molecule B7-H3. Furthermore, down-regulation of lncRNA TUG1 decreased the level of GATA3 in CD4+T cells and was associated with miR-29c/B7-H3 axis. Moreover, the dual-luciferase reporter assay confirmed that lncRNA TUG1 serves as a competing endogenous RNA to sponge miR-29c. According to the rescue experiment, lncRNA TUG1 regulated Th2 cell differentiation via miR-29c. These data suggest that lncRNA TUG1 in macrophages regulates Th2 cell differentiation via miR-29c/B7-H3 axis.