Dying cells are capable of activating the innate immune system and inducing a sterile inflammatory response. Here, we show that necrotic cells are sensed by the Nlrp3 inflammasome resulting in the subsequent release of the proinflammatory cytokine IL-1β. Necrotic cells produced by pressure disruption, hypoxic injury, or complement-mediated damage were capable of activating the Nlrp3 inflammasome. Nlrp3 inflammasome activation was triggered in part through ATP produced by mitochondria released from damaged cells. Neutrophilic influx into the peritoneum in response to necrotic cells in vivo was also markedly diminished in the absence of Nlrp3. Nlrp3-deficiency moreover protected animals against mortality, renal dysfunction, and neutrophil influx in an in vivo renal ischemic acute tubular necrosis model. These findings suggest that the inhibition of Nlrp3 inflammasome activity can diminish the acute inflammation and damage associated with tissue injury.
To the Editor: With great interest, we have read the study by Loverre et al. The authors show by means of immunostaining that numerous IL-17+CD4+ cells are present in renal biopsies during T-cell-mediated rejection (TCMR) and demonstrate that tubular epithelial cells (TECs) represent a significant source for IL-17 in antibody-mediated rejection (ABMR; Ref. 1Loverre A Tataranni T Castellano G et al.IL-17 expression by tubular epithelial cells in renal transplant recipients with acute antibody-mediated rejection.Am J Transplant. 2011; 11: 1248-1259Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar). We have some concerns regarding the specificity of the immunostaining. Indeed, antibodies from different suppliers can give conflicting results. We recently investigated the protein expression of IL-17 in TCMR and ABMR and found that the majority of IL-17+ cells were neutrophils or mast cells and that IL-17+ T-lymphocytes were hardly present. Also, we did not observe any IL-17 protein expression in TECs (2Yapici U Kers J Bemelman FJ et al.Interleukin-17 positive cells accumulate in renal allografts during acute rejection and are independent predictors of worse graft outcome.Transpl Int. 2011; 24: 1008-1017Crossref PubMed Scopus (32) Google Scholar). For this study, five anti-IL-17 antibodies from four different suppliers were tested on tonsillar tissue: R&D Systems polyclonal goat antihuman IL-17 (AF-317-NA), Santa Cruz polyclonal rabbit antihuman IL-17 (SC7927), Peprotech polyclonal rabbit and goat antihuman IL-17 (500-P07 and 500-P07G) and eBioscience monoclonal mouse antihuman IL-17 (eBio64Dec17). With diaminobenzidine (DAB) staining, the antibodies from Peprotech and eBioscience did not show any interpretable staining. The Santa Cruz antibody showed an almost diffuse staining of all lymphoid cells and also abundant nuclear and cytoplasmic staining of squamous epithelium (Figure 1A). In contrast, the R&D Systems antibody showed positivity in part of the lymphoid cells and almost no background staining (Figure 1B). Double stainings for IL-17 from both suppliers, using Vector blue, with CD3 (T-lymphocytes) or tryptase (mast cells), using vector red, showed only presence of IL-17+ mast cells and no IL-17+ T-lymphocytes. With the Santa Cruz antibody, there was a prominent nonspecific background staining (Figures 1C–F). In renal biopsies, the DAB staining for the Santa Cruz antibody showed a cytoplasmic staining pattern in part of the TECs and in a few graft infiltrating inflammatory cells. In contrast, the R&D Systems antibody was positive in more inflammatory cells and did not show any TEC staining (Figures 1G and H). Double stainings of the renal biopsies showed similar results as in tonsillar tissue (Figures 1I–L). De Boer and colleagues also extensively validated IL-17 immunostainings before and obtained the same results. They chose the R&D Systems antibody and characterized IL-17+ infiltrates in atherosclerotic plaques, where they could not find any IL-17+ T-lymphocytes (3de Boer OJ van der Meer JJ Teeling P et al.Differential expression of interleukin-17 family cytokines in intact and complicated human atherosclerotic plaques.J Pathol. 2010; 220: 499-508Crossref PubMed Scopus (172) Google Scholar). Also, in psoriatic skin lesions only an occasional IL-17+ T-lymphocyte could be detected (4Res PC Piskin G de Boer OJ et al.Overrepresentation of IL-17A and IL-22 producing CD8 T cells in lesional skin suggests their involvement in the pathogenesis of psoriasis.PLoS One. 2010; 5: e14108Crossref PubMed Scopus (250) Google Scholar). Our results are in line with these studies. In summary, Santa Cruz and R&D Systems IL-17 antibodies produce conflicting results. Adequate selection and optimization of the antibodies using appropriate controls are critical before drawing definitive conclusions. The authors of this manuscript have no conflicts of interest to disclose as described by the American Journal of Transplantation.
Abstract To determine the role of IL-1 in the host defense against pneumonia, IL-1R type I-deficient (IL-1R−/−) and wild-type (Wt) mice were intranasally inoculated with Streptococcus pneumoniae. Pneumonia resulted in elevated IL-1α and IL-1β mRNA and protein levels in the lungs. Survival rates did not differ between IL-1R−/− and Wt mice after inoculation with 5 × 104 or 2 × 105 CFU. At early time points (24 and 48 h) IL-1R−/− mice had 2-log more S. pneumoniae CFU in lungs than Wt mice; at 72 h bacterial outgrowth in lungs was similar in both groups. Upon histopathologic examination IL-1R−/− mice displayed a reduced capacity to form inflammatory infiltrates at 24 h after the induction of pneumonia. IL-1R−/− mice also had significantly less granulocyte influx in bronchoalveolar lavage fluid at 24 h after inoculation. Since TNF is known to enhance host defense during pneumonia, we determined the role of endogenous TNF in the early impairment and subsequent recovery of defense mechanisms in IL-1R−/− mice. All IL-1R−/− mice treated with anti-TNF rapidly died (no survivors (of 14 mice) after 4 days), while 10-day survival in IL-1R−/− mice (control Ab), Wt mice (anti-TNF), and Wt mice (control Ab) was 7 of 13, 3 of 14, and 12 of 13, respectively. These data suggest that TNF is more important for host defense against pneumococcal pneumonia than IL-1, and that the impaired early host defense in IL-1R−/− mice is compensated for by TNF at a later phase.
Treatments aimed at inhibition of tumor necrosis factor (TNF) in patients with sepsis have been unsuccessful. Up to 50% of such patients suffer from pneumonia. To determine the effect that treatment with anti-TNF has on pneumococcal pneumonia, mice were intranasally inoculated with Streptococcus pneumoniae and, 25 h later, treated with 1 of the following: (1) control antibody, (2) anti-TNF, (3) ceftriaxone (CEF) with control antibody, or (4) CEF with anti-TNF. In the absence of treatment with CEF, mice displayed high bacterial loads in lungs, and all of these mice died within 5 days after inoculation. Anti-TNF did not influence these outcomes. In contrast, 60% of mice treated with CEF alone survived. Anti-TNF administered together with CEF reduced survival to 40% and was associated with enhanced bacterial outgrowth. These data suggest that treatment with anti-TNF impairs the therapeutic efficacy of CEF during pneumococcal pneumonia.
