免疫学

Experimental pneumonia models are important tools to study the pathophysiology of lung inflammation caused by microbial infections and the efficacy of (novel) drugs. We have applied a murine model of pneumonia induced by Pseudomonas (P.) aeruginosa infection to study acute host antibacterial defense in lungs, and assess epithelial cell specific responses as well as leukocyte recruitment to the alveolar space. To study host responses during disseminating pneumonia, we also applied a model of infecting mice with hypermucoviscous Klebsiella (K.) pneumoniae. In the latter model, K. pneumoniae is restricted to lung during the early phase of infection and at the later time points disseminates to the circulation and distal organs resulting in sepsis. Detailed procedures for induction of pneumonia in mice by Pseudomonas and Klebsiella and for isolation and analysis of infected organs, bronchoalveolar fluid, and bronchial brushes are provided in this article.

CD49b is a member of the integrin family, expressed on basophils, natural killer (NK) cells and a subset CD4⁺ T cells in the spleen. This protocol describes the adoptive transfer of basophil-enriched CD49b⁺ cells obtained from mouse spleens by magnetic enrichment. This protocol can be used to assess the contribution of basophils or basophil-derived mediators to a certain immune response.

Here we describe a method to test bacterial adhesion to paraffin embedded tissue sections. This method allows examining binding of different bacterial strains, transfected with a fluorescent protein reporter plasmid to various tissues, to better understand different mechanisms such as colonization. This assay provides a more physiological context to bacterial binding, than would have been achieved using adhesion assays to cell lines. The sections can be imaged using fluorescent microscopy and adhesion of various bacterial strains can be quantified and tested, simultaneously.

Cellular infection with tick-borne flaviviruses (TBFVs) results in activation of the interferon (IFN) signaling pathway and subsequent upregulation of numerous genes termed IFN stimulated genes (ISGs) (Schoggins et al., 2011). Many ISGs function to prevent virus pathogenesis by acting in a broad or specific manner through protein-protein interactions (Duggal and Emerman, 2012). The potency of the IFN signaling response determines the outcome of TBFV infection (Best, 2017; Carletti et al., 2017). Interestingly, data from our lab show that TBFV replication is significantly restricted in cells of the reservoir species Peromyscus leucopus thereby suggesting a potent antiviral response (Izuogu et al., 2017). We assessed the relative contribution of IFN signaling to resistance in P. leucopus by knocking down a major transcription factor in the IFN response pathway. Signal transducer and activator of transcription 1 (STAT1) was specifically targeted in P. leucopus cells by shRNA technology. We further tested the impact of gene knockdown on the ability of cells to respond to IFN and restrict virus replication; the results indicate that when STAT1 expression is altered, P. leucopus cells have a decreased response to IFN stimulation and are significantly more susceptible to TBFV replication.

Collagen is one of the foremost components of tissue extracellular matrix (ECM). It provides strength, elasticity and architecture to the tissue enabling it to bear the wear and tear from external factors like physical stress as well as internal stress factors like inflammation or other pathological conditions. During normal pregnancy or pregnancy related pathological conditions like preterm premature rupture of membranes (PPROM), collagen of the fetal membrane undergoes dynamic remodeling defining biochemical properties of the fetal membrane. The protocol in this article describes the histochemical method to stain total collagen by Picrosirius red stain which is a simple, quick and reliable method. This protocol can be used on paraformaldehyde (PFA) and formaldehyde fixed paraffin embedded tissue sections. We further describe the staining and distribution of collagen in different mouse reproductive tissues and also demonstrate how this technique in combination with polarization microscopy is useful to detect the distribution of different subtypes of collagen.

This urinary tract infection model was used to monitor the efficacy of a new virulence factor of the uropathogenic Escherichia coli strain CFT073 in vivo. The new virulence factor which we designated TIR-containing protein C (TcpC) blocks Toll-like receptor signaling and the NLRP3 inflammasome signaling cascade by interacting with key components of both pattern recognition receptor systems (Cirl et al., 2008; Waldhuber et al., 2016). We infected wild type and knock-out mice with wildtype CFT073 and a mutant CFT073 strain lacking tcpC. This protocol describes how the mice were infected, how CFT073 was prepared and how the infection was monitored. The protocol was derived from our previously published work and allowed us to demonstrate that TcpC is a powerful virulence factor by increasing the bacterial burden of CFT073 in the urine and kidneys. Moreover, TcpC was responsible for the development of kidney abscesses since infection of mice with wildtype but not tcpC-deficient CFT073 mutants caused this complication.

Aspergillus fumigatus is a ubiquitous fungal pathogen that forms airborne conidia. The process of restricting conidial germination into hyphae by lung leukocytes is critical in determining infectious outcomes. Tracking the outcome of conidia-host cell encounters in vivo is technically challenging and an obstacle to understanding the molecular and cellular basis of antifungal immunity in the lung. Here, we describe a method that utilizes a genetically engineered Aspergillus strain [called FLARE (Jhingran et al., 2012; Espinosa et al., 2014; Heung et al., 2015)] to monitor conidial phagocytosis and killing by leukocytes within the lung environment at single encounter resolution.

After activation, T cells differentiate into different T helper (Th) subsets, namely Th1, Th2, and Th17. These different Th subsets are associated with the production of particular cytokines endowing them with different functions. In immunity against helminth infections the Th2 cell subset plays an important role. Th2 cells typically produce IL-4, IL-5, IL-13, and IL-9 resulting in antibody-isotype switching to IgE, eosinophilia, basophilia, mucin production, and smooth muscle cell hyperactivity. Here we analyze the development of the pathogen specific Th2 immune responses in mice after infection with the helminth parasite, Heligmosomoides polygyrus bakeri, the induction of innate lymphoid cells type 2 (ILC2) and the activation of the inflammasome in macrophages by excretory/secretory products of Heligmosomoides polygyrus bakeri.

Macrophage recognition of Candida albicans (C. albicans) is facilitated by pattern recognition receptors that interact with the fungal pathogen associated molecular patterns (PAMPs). Dectin-1 is the major macrophage receptor that is known to recognize fungal Beta-glucans leading to induction of various immune responses. This receptor is also known to be required for in vivo protection against C. albicans (Taylor et al., 2007). We recently showed that the Dectin-1 mediated protection in vivo is strain-dependent, and that C. albicans can adapt to modulate immune recognition by Dectin-1 (Marakalala et al., 2013). In vitro analysis, however, showed a Dectin-1-dependent and pro-inflammatory responses against all strains tested. This protocol describes in detail the in vitro analysis used in the paper. In particular, methods involved in fluorescent labeling of live C. albicans, quantification of macrophage binding of the pathogen, and pro-inflammatory responses to yeast and hyphal forms of the fungi are described.

During viral infections Interferon-α (IFN-α) is expressed by infected host cells. IFN-α binds to its receptor (IFNAR1/2), which leads to the activation of downstream signaling via JAK-STAT. This signaling cascade results in the expression of several hundred different genes, so called interferon-stimulated gene, which lead to an antiviral state of the infected and the neighboring cells.