15 research outputs found
Toll-like receptor-4 differentially mediates intestinal and extra-intestinal immune responses upon multi-drug resistant Pseudomonas aeruginosa association of IL10−/− mice with chronic colitis
Background Infections with multi-drug resistant (MDR) Gram-negative bacteria
including Pseudomonas aeruginosa (PA) have become a serious threat
particularly in hospitalized patients with immunopathological co-morbidities.
The well-balanced interplay between immune cells, pattern recognition
receptors such as Toll-like receptor (TLR)-4 sensing lipopolysaccharide from
Gram-negative bacteria including PA, and evolving pathways is crucial to
prevent the host from invading (opportunistic) pathogens. Information
regarding the molecular mechanisms underlying the interactions between
intestinal carriage of MDR PA and host immunity during chronic large
intestinal inflammation is scarce, however. Methods and results We therefore
perorally challenged conventionally colonized TLR4-deficient IL10−/− mice and
IL10−/− counterparts displaying comparably severe chronic colitis with a
clinical MDR PA strain. PA could more sufficiently establish in the intestinal
tract of TLR4-deficient IL10−/− mice until day 14 postinfection (p.i.),
whereas within 48 h the majority of IL10−/− mice had already expelled the
opportunistic pathogen from their guts. Intestinal colonization properties of
PA in TLR4-deficient IL10−/− mice were associated with distinct genotype-
dependent differences in gut microbiota compositions before challenge given
that TLR4-deficient IL10−/− mice harbored more fecal enterobacteria and
enterococci, but lower Clostridium/Eubacterium burdens. At day 14 p.i., PA-
induced increases in colonic immune cells such as macrophages, monocytes and
T-lymphocytes could be observed in TLR4-deficient IL10−/− mice, but not
IL10−/− counterparts, that were accompanied by a more distinct secretion of
IFN-γ in the colon and TNF in the mesenteric lymph nodes (MLN) of the former
as compared to the latter. Conversely, splenic TNF levels were lower in
TLR4-deficient IL10−/− mice as compared to IL10−/− controls at day 14 p.i.
Interestingly, more pronounced apoptotic responses could be assessed in
colonic epithelia of PA-challenged IL10−/− mice only. This was paralleled by
enhanced pro-inflammatory cytokine secretion not only in the intestines, but
also in extra-intestinal compartments of IL10−/− mice as indicated by
increased concentrations of nitric oxide in the colon, IFN-γ in the MLN and
IL-12p70 in the spleen at day 14 p.i. Conclusions Under chronic intestinal
inflammatory conditions including IL10−/− colitis MDR PA-association results
in well-orchestrated TLR4-dependent immune responses both in intestinal and
extra-intestinal compartments. Further studies should unravel the underlying
molecular mechanisms in more detail
Immune responses upon Campylobacter jejuni infection of secondary abiotic mice lacking nucleotide-oligomerization-domain-2
Background Campylobacter jejuni infections are of rising importance worldwide.
Given that innate immune receptors including nucleotide-oligomerization-
domain-2 (Nod2) are essentially involved in combating enteropathogenic
infections, we here surveyed the impact of Nod2 in murine campylobacteriosis.
Methods and results In order to overcome physiological colonization resistance
preventing from C. jejuni infection, we generated secondary abiotic Nod2−/−
and wildtype (WT) mice by broad-spectrum antibiotic treatment. Mice were then
perorally infected with C. jejuni strain 81-176 on 2 consecutive days and
could be stably colonized by the pathogen at high loads. Notably, Nod2
deficiency did not affect gastrointestinal colonization properties of C.
jejuni. Despite high intestinal pathogenic burdens mice were virtually
uncompromised and exhibited fecal blood in single cases only. At day 7
postinfection (p.i.) similar increases in numbers of colonic epithelial
apoptotic cells could be observed in mice of either genotype, whereas C.
jejuni infected Nod2−/− mice displayed more distinct regenerative properties
in the colon than WT controls. C. jejuni infection was accompanied by
increases in distinct immune cell populations such as T lymphocytes and
regulatory T cells in mice of either genotype. Increases in T lymphocytes,
however, were less pronounced in large intestines of Nod2−/− mice at day 7
p.i. when compared to WT mice, whereas colonic numbers of B lymphocytes were
elevated in WT controls only upon C. jejuni infection. At day 7 p.i., colonic
pro-inflammatory mediators including nitric oxide, TNF, IFN-γ and IL-22
increased more distinctly in Nod2−/− as compared to WT mice, whereas C. jejuni
induced IL-23p19 and IL-18 levels were lower in the large intestines of the
former. Converse to the colon, however, ileal concentrations of nitric oxide,
TNF, IFN-γ, IL-6 and IL-10 were lower in Nod2−/− as compared to WT mice at day
7 p.i. Even though MUC2 was down-regulated in C. jejuni infected Nod2−/− mice,
this did not result in increased pathogenic translocation from the intestinal
tract to extra-intestinal compartments. Conclusion In secondary abiotic mice,
Nod2 signaling is involved in the orchestrated host immune responses upon C.
jejuni infection, but does not control pathogen loads in the gastrointestinal
tract
Mycobacterium tuberculosis infection modulates adipose tissue biology
Mycobacterium tuberculosis (Mtb) primarily resides in the lung but can also
persist in extrapulmonary sites. Macrophages are considered the prime cellular
habitat in all tissues. Here we demonstrate that Mtb resides inside adipocytes
of fat tissue where it expresses stress-related genes. Moreover, perigonadal
fat of Mtb-infected mice disseminated the infection when transferred to
uninfected animals. Adipose tissue harbors leukocytes in addition to
adipocytes and other cell types and we observed that Mtb infection induces
changes in adipose tissue biology depending on stage of infection. Mice
infected via aerosol showed infiltration of inducible nitric oxide synthase
(iNOS) or arginase 1 (Arg1)-negative F4/80+ cells, despite recruitment of
CD3+, CD4+ and CD8+ T cells. Gene expression analysis of adipose tissue of
aerosol Mtb-infected mice provided evidence for upregulated expression of
genes associated with T cells and NK cells at 28 days post-infection.
Strikingly, IFN-γ-producing NK cells and Mtb-specific CD8+ T cells were
identified in perigonadal fat, specifically CD8+CD44-CD69+ and CD8+CD44-CD103+
subpopulations. Gene expression analysis of these cells revealed that they
expressed IFN-γ and the lectin-like receptor Klrg1 and down-regulated CD27 and
CD62L, consistent with an effector phenotype of Mtb-specific CD8+ T cells.
Sorted NK cells expressed higher abundance of Klrg1 upon infection, as well.
Our results reveal the ability of Mtb to persist in adipose tissue in a
stressed state, and that NK cells and Mtb-specific CD8+ T cells infiltrate
infected adipose tissue where they produce IFN-γ and assume an effector
phenotype. We conclude that adipose tissue is a potential niche for Mtb and
that due to infection CD8+ T cells and NK cells are attracted to this tissue
Facilitated Peptide Transport via the Mucosal Epithelium
A hallmark of autoimmunity is the breakdown of tolerance and generation of
effector responses against self-antigens. Re-establishment of tolerance in
autoimmune disorders was always the most desired treatment option; however,
despite many efforts, clinical trials have been largely unsuccessful. This
also applies to the generation of oral tolerance, which seems to be a default
response type of the mucosa-associated lymphoid tissues to harmless antigens.
In this study, we report improved efficacy of oral tolerance induction by
coupling antigen with the newly identified mucosal carrier peptide 13C.
Antigen coupled to 13C is efficiently taken up in the gastrointestinal tract
and could be visualized in cells of the lamina propria. Oral, rectal, or nasal
treatment effectively induced the proliferation of antigen-specific T cells
with some increase in the frequency of regulatory T cells. In a model of
delayed-type hypersensitivity, especially intrarectal tolerization treatment
resulted in reduced footpad swelling, demonstrating a moderate tolerogenic
effect of mucosal treatment with 13C coupled antigen. Coupling of antigens to
a transmucosal carrier, therefore, is a promising tool to improve the efficacy
of vaccination via mucosal surfaces
Anti-RANKL treatment inhibits erosive joint destruction and lowers inflammation but has no effect on bone formation in the delayed-type hypersensitivity arthritis (DTHA) model
BACKGROUND: The aims of the present study were to determine the relationship between bone destruction and bone formation in the delayed-type hypersensitivity arthritis (DTHA) model and to evaluate the effect of receptor activator of nuclear factor κB ligand (RANKL) blockade on severity of arthritis, bone destruction, and bone formation. METHODS: DTHA was induced in C57BL/6 mice. Inflammation, erosive joint damage, and new bone formation were semiquantitatively scored by histology. Osteoclast activity was assessed in vivo, and messenger RNA (mRNA) expression of mediators of bone destruction and bone formation were analyzed by mRNA deep sequencing. Serum concentrations of tartrate-resistant acid phosphatase 5b, carboxy-terminal telopeptide I (CTX-I), matrix metalloproteinase 3 (MMP3), and serum amyloid P component (SAP) were determined by enzyme-linked immunosorbent assay. Anti-RANKL monoclonal antibody treatment was initiated at the time of immunization. RESULTS: Bone destruction (MMP3 serum levels, cathepsin B activity, and RANKL mRNA) peaked at day 3 after arthritis induction, followed by a peak in cartilage destruction and bone erosion on day 5 after arthritis induction. Periarticular bone formation was observed from day 10. Induction of new bone formation indicated by enhanced Runx2, collagen X, osteocalcin, MMP2, MMP9, and MMP13 mRNA expression was observed only between days 8 and 11. Anti-RANKL treatment resulted in a modest reduction in paw and ankle swelling and a reduction of serum levels of SAP, MMP3, and CTX-I. Destruction of the subchondral bone was significantly reduced, while no effect on bone formation was seen. CONCLUSIONS: Anti-RANKL treatment prevents joint destruction but does not prevent new bone formation in the DTHA model. Thus, although occurring sequentially during the course of DTHA, bone destruction and bone formation are apparently not linked in this model
Persistent anthrax as a major driver of wildlife mortality in a tropical rainforest
Anthrax is a globally important animal disease and zoonosis. Despite this, our current knowledge of anthrax ecology is largely limited to arid ecosystems, where outbreaks are most commonly reported. Here we show that the dynamics of an anthrax-causing agent, Bacillus cereus biovar anthracis, in a tropical rainforest have severe consequences for local wildlife communities. Using data and samples collected over three decades, we show that rainforest anthrax is a persistent and widespread cause of death for a broad range of mammalian hosts. We predict that this pathogen will accelerate the decline and possibly result in the extirpation of local chimpanzee (Pan troglodytes verus) populations. We present the epidemiology of a cryptic pathogen and show that its presence has important implications for conservation
IL-35-producing B cells are critical regulators of immunity during autoimmune and infectious diseases
International audienceB lymphocytes have critical roles as positive and negative regulators of immunity. Their inhibitory function has been associated primarily with interleukin 10 (IL-10) because B-cell-derived IL-10 can protect against autoimmune disease and increase susceptibility to pathogens. Here we identify IL-35-producing B cells as key players in the negative regulation of immunity. Mice in which only B cells did not express IL-35 lost their ability to recover from the T-cell-mediated demyelinating autoimmune disease experimental autoimmune encephalomyelitis (EAE). In contrast, these mice displayed a markedly improved resistance to infection with the intracellular bacterial pathogen Salmonella enterica serovar Typhimurium as shown by their superior containment of the bacterial growth and their prolonged survival after primary infection, and upon secondary challenge, compared to control mice. The increased immunity found in mice lacking IL-35 production by B cells was associated with a higher activation of macrophages and inflammatory T cells, as well as an increased function of B cells as antigen-presenting cells (APCs). During Salmonella infection, IL-35- and IL-10-producing B cells corresponded to two largely distinct sets of surface-IgM(+)CD138(hi)TACI(+)CXCR4(+)CD1d(int)Tim1(int) plasma cells expressing the transcription factor Blimp1 (also known as Prdm1). During EAE, CD138(+) plasma cells were also the main source of B-cell-derived IL-35 and IL-10. Collectively, our data show the importance of IL-35-producing B cells in regulation of immunity and highlight IL-35 production by B cells as a potential therapeutic target for autoimmune and infectious diseases. This study reveals the central role of activated B cells, particularly plasma cells, and their production of cytokines in the regulation of immune responses in health and disease