Furthermore, investigations show that for gp96, non-specific endocytosis/pinocytosis Sotrastaurin solubility dmso mechanisms account for a fraction of internalization.[39] Heat-shock proteins deliver peptides as cargo to DC (Fig. 1) leading to MHC presentation for priming of adaptive immunity.[40] Increased levels of pathogen-derived hsp caused by inflammatory stimuli such as fever, result in a concomitant increase in pathogen-specific antigens carried as hsp complexes.[41] The uptake of hsp complexes by DC enables efficient capture and presentation of pathogen-specific antigens and the mounting of a specific immune response against the infectious

agent through the generation of CD4+ T-cell responses.[42] The capture of pathogen-specific antigens ‘chaperoned’ in hsp complexes also results in their uptake and MHC class I restricted

presentation to specific T-cells, so eliciting CD8+ cytotoxic T-cell responses.[43] It has been shown through the use of inhibitors, that hsp90 plays a significant natural role in chaperoning GSK2118436 in vivo antigenic peptides in presentation.[44] Human DC pulsed with peptide-loaded mycobacterial hsp70 generate potent antigen-specific cytotoxic T-cell responses, dependent on an hsp70-stimulated calcium signalling cascade.[45] Delivery of peptides is achieved significantly through extracellular hsp binding to cellular receptors, followed by internalization.[46] Antigens need to be bound or linked to hsp to facilitate uptake, simple mixing is not adequate. The hsp70–peptide complexes reach endosomal compartments

that fuse with vesicles containing recycling MHC class I–peptide complexes. Protein fragments chaperoned by hsp and not intact proteins are sufficient for priming CD8+ T-cell responses.[47] Highly purified human recombinant hsp70 enhances cross-presentation of exogenous antigens on MHC class I resulting in better Niclosamide antigen-specific T-cell stimulation.[48] Here T-cell stimulation was a function of the degree of complex formation between hsp70 and peptides and correlated with improved antigen delivery to endosomal compartments. hsp70 enhanced cross-presentation by different APC including DC and B cells and antigen-specific T-cell activation occurred in the absence of innate signals transmitted by hsp70.[48] Heat shock protein 90-mediated cross-presentation of ovalbumin-derived antigens involves binding of hsp90–ovalbumin complexes to Scavenger Receptor expressed by Endothelial Cells-I on the surface of APC.[49] Internalization is driven through a regulated, endocytic pathway.[49] Peptides are loaded either directly onto MHC class I in endosomes, or undergo cytosomal processing by aminopeptidases and proteases. Extracellular hsp90 can therefore convey antigenic peptides through an efficient endocytosis pathway in APC and facilitate presentation in a regulated manner.[49] Heat-shock proteins can also mediate by the same mechanism cross-presentation of exogenous HIV antigens.

Thus, TLR4 is a target for treatment of sepsis (Leaver et al., 2007; Spiller et al., 2008; Roger et al., 2009). The increased resistance of TLR4 KO mice to lethal infection with V. vulnificus is likely due to attenuation of the TNFα response that, as demonstrated with TNFα KO mice, is deleterious during V. vulnificus infection. Results of ex vivo assays show that TNFα production is significantly reduced in supernatants from TLR4 KO mouse blood and splenocytes stimulated with V. vulnificus cells. If a similar reduction of TNFα occurs in vivo due to TLR4 deficiency, this could mitigate an early, exaggerated inflammatory response,

thus contributing to the improved survival of TLR4 KO mice. In contrast to TLR4 or TNFα deficiency, MyD88 deficiency is deleterious to mice infected with V. vulnificus. These results appear to be counterintuitive because the harmful TNFα response is strongly attenuated in the absence Enzalutamide in vitro selleck kinase inhibitor of MyD88 (Weighardt et al., 2002; Power et al., 2004). Indeed, Weighardt et al. (2002) showed that MyD88 deficiency enhances the resistance of mice to sepsis due to polymicrobial infection. However, various studies have shown that MyD88-dependent TLR signaling is required for activation of protective host responses needed for immune cell recruitment and subsequent pathogen clearance due to monomicrobial infection (Power et al., 2004; Khan et al., 2005;

Weiss et al., 2005). It is plausible that the beneficial effect conferred by ablation of TLR4 signaling in V. vulnificus-infected MyD88 KO mice is negated by the ablation of signaling of

other TLR(s) that are necessary to control infection. Preliminary results suggest that although MyD88 KO mice have a higher burden of V. vulnificus Methane monooxygenase in their blood during early infection, they succumb to infection at a slower rate than WT mice (L.V. Stamm, unpublished data). Thus, while a reduced inflammatory response promotes short-term survival, infected MyD88 KO mice ultimately die presumably due to their inability to control V. vulnificus replication, which results in tissue damage via elaboration of multiple virulence factors (Gulig et al., 2005). Previous in vitro studies have shown that recombinant-produced V. vulnificus lipoprotein and FlaB are recognized by TLR2 and TLR5, respectively (Lee et al., 2006; Goo et al., 2007). While the roles of TLR2 and TLR5 in the host response to V. vulnificus infection remain to be elucidated, it is tempting to speculate that TLR2 may be a key player due to the abundance of TLR2 agonists (∼100 lipoproteins) synthesized by this bacterium (Babu & Sankaran, 2005). Additionally, because TLR2 is constitutively expressed at a high level by blood phagocytes, the TNFα produced by WT mouse blood stimulated with V. vulnificus cells may be the net result of MyD88-dependent TLR2 and TLR4 signaling. It should be noted that this hypothesis is based on results of ex vivo assays that used inactivated V.

Interestingly, MoDC that was incubated with PIC-CM prior to coculturing them with allogeneic PBMC generated a highly increased see more release of IFN-γ in MLR culture supernatants. Both changes in MoDCs, i.e. upregulation of CD40, CD86, and increased MLR stimulation, were abrogated by blocking IFN-β. Surprisingly, MoDC incubated with PIC-CM did not induce IL-12p70 secretion; however, previous data showed that under certain conditions, IL-12p70 can be dispensable for IFN-γ induction. Indeed, in some virus infections, the lack of IL-12 has little or no effect on the induction

of Th1 immunity and systemic production of IL-12p70 could not be detected after in vivo administration of poly I:C, whereas poly I:C was superior at inducing systemic type I IFNs and Th1 immune response [42-45]. Murine BMDCs also secreted higher levels of IL-12p70 when they were matured in the presence of PAU-B16 CM. Therefore, a novel aspect of the use of dsRNA mimetics in cancer immunotherapy can be assumed: when tumor

cells are activated with dsRNA ligands, they secrete IFN-β at levels that are capable of improving the maturation state and function of DCs, promoting a Th1 response that could be independent of the induction of IL-12. Tumor-derived factors significantly alter the generation of DCs from hematopoietic progenitors, increase the accumulation of VX-809 research buy myeloid suppressor cells, and inhibit DCs maturation [22, 23]. When MoDCs were matured with different TLR ligands in the presence of tumor CM, expression of co-stimulatory molecules, secretion of IL-12p70, and induction of IFN-γ in MLR were significantly diminished. In contrast, when the maturation was done in the presence of PIC-CM, all OSBPL9 these parameters were improved. Indeed, TLR-induced IL-12p70 secretion by DC has been

shown to depend on a type I IFN autocrine–paracrine loop [26]. Thus, the simultaneous presence of IFN-β plus the exogenously added TLR ligand, and/or other factors present in PIC-CM such as HMGB1 or other cytokines, could be producing a synergistic effect on maturing MoDCs that can be readily observed in the enhanced values of secreted IL-12p70 and the better capacity of driving an IFN-γ response in the MLR. Similar results were obtained in our previous work, in which murine prostate adenocarcinoma and melanoma cells (TRAMPC2 and B16, respectively) secrete low but reliably detected levels of IFN-β upon TLR4 activation [19]. These low levels of IFN-β were enough to enhance the expression of co-stimulatory molecules on BMDCs as well as to increase the levels of IL-12 secreted. In addition, the frequency of CD11c+ tumor infiltrating cells expressing IL-12 was increased in mice bearing LPS-B16 tumors [19].

Flow cytometric analysis was performed and positive events, i.e. antigen-specific T cells, were identified as a percentage of CD3+ CD8+ T cells. At least 50 000 events were obtained in the CD3+ CD8+ CD4− CD13−

CD19− population. The following antibodies (Abs) obtained from Beckman Coulter were used: anti-CD3-phycoerythrin-Texas red (clone selleck antibody CHT1) and anti-CD8α-FITC (clone T8) for positive gating, and anti-CD4-PCy5 (clone 13B8.2), anti-CD13-Pcy5 (clone SJ1D1) and anti-CD19-Pcy5 (clone J4.119) for negative gating. Positive tetramer staining was compared with staining with the iTag negative control tetramer. This gating strategy has been found to reliably identify ‘low-frequency’ events, for example melanoma-specific and Melan-A/melanoma antigen recognized by T-cell-1 (MART-1)-1 reactive CD8+ T cells, if the negative control tetramer reagent (loaded with an irrelevant peptide) is used to set the negative gate.22 Flow cytometry analysis was performed using an FC500 flow cytometer from Beckman Coulter (Krefeld, Germany). Eighty-eight overlapping peptides from TB10.4 were tested for binding

to five HLA-A molecules (A*0101, A*0201, A*0301, A*1101 and A*2402) and three HLA-B molecules (B*0702, B*0801 Quizartinib chemical structure and B*1501). Binding to each allele is reported as a percentage relative to a positive control peptide for the respective MHC class I allele. With a cut-off of 20% binding as compared with the positive control peptide, we identified the following numbers of positive binding epitopes: two of 88 for A*0101, 17 of 88 for A*0201, two of 88 for A*0301, three of 88 for A*1101, 10 of 88 for A*2402, seven of

88 for B*0702, zero of 88 for B*0801 and 12 of 88 for B*1501 (Fig. 1, Table 1). The alleles HLA-A*0201 and HLA-A*2402 were among the most frequent MHC class I–peptide binders; they bound 20% and 11% of the candidate peptides, respectively. Also, HLA- B*1501 was among the top MHC class I-binding alleles; it bound to 14% of the TB10.4 peptide library. The prediction program syfpeithi (http://www.syfpeithi.de) picked up most TB10.4 epitopes for HLA-A*0201, A*2402 and A*1101; 17 of 17, Cytidine deaminase five of seven and two of three binding epitopes showed a syfpeithi score ≥ 10. For other MHC class I alleles, the program showed a lower success rate; for example, for B*0701 and B*1510, one of seven and five of 12 binding epitopes showed a syfpeithi score ≥ 10. Thirty-three of 88 candidate peptides bound at least to one MHC class I allele; the epitopes could be found throughout the whole amino acid sequence but with some clustering at the N- and C-termini (Fig. 2). Screening of TB10.4 peptides for binding to the eight most frequent Caucasian alleles revealed extensive cross-binding of the identical or closely related peptides to different MHC class I molecules.

For instance, IL-7 is essential for the generation of murine pre-B cells and the IL-7 receptor synergizes with the pre-BCR to activate pre-B cell cycling 28, 29. This dual regulation of early B-cell generation might be important to prevent an uncontrolled proliferation of pre-B or

autoreactive B cells, while allowing a certain magnitude of cell cycling, which is followed by the rearrangement selleck screening library of the LC genes. Thus, regulating the concentration of growth factors in the microenvironment or altering the responsiveness of developing B cells to these factors seems to control the switch from proliferation to differentiation (i.e. LC gene rearrangement) in response to pre-BCR or autoreactive BCR signaling. Conversely, combining autoreactive BCRs with elevated expression of growth factors

such as IL-7 might lead to lymphoproliferative and/or autoimmune diseases as suggested by transgenic over-expression of IL-7 30. It would be interesting to test whether the BCRs of these immature B-cell lymphomas possess increased autoreactivity and whether LY2606368 this is involved in the increased lymphoproliferation. Altogether, understanding the positive role of autoreactivity in precursor B-cell proliferation not only highlights the importance of pre-BCR expression for early B-cell selection but might also help to explain the molecular mechanisms that underlie the development of autoimmune and lymphoproliferative diseases. Our study demonstrates the importance of autoreactivity for proper B-cell development with the pre-BCR

being an invariantly autoreactive Cyclin-dependent kinase 3 receptor. In the presence of a strongly recognized antigen the self-reactivity of the pre-BCR can be substituted by an autoreactive BCR to allow efficient generation of B cells. Thus, it is conceivable that at the early immature B-cell stage, cells bearing an autoreactive BCR may continue to proliferate and to recombine their LCs just as their pre-B cell predecessors do. After having changed their autoreactive specificity by receptor editing, such BCRs may get stably expressed on the surface of immature B cells, which then proceed in development. Our results are reminiscent of a hypothesis published by Niels Jerne in the very first issue of this journal 40 years ago, in which he proposed the selection of escape mutants through the initial expansion and subsequent negative selection of progenitor cells expressing germ line encoded autoreactive receptors as a mechanism of somatic antibody diversification 31. Mb1-lox-GFP mice 18, λ5−/− mice 10, 3-83Igi mice carrying the pre-rearranged 3-83Hi/33-83κi Ig gene segments 14 and mice carrying the B1-8Hi/3-83κi Ig gene segments 15 were used in this study. All mice used for the generation of HSCs were backcrossed on H-2d background. Rag-2/λC−/− mice 17, either on Balb/C or BL/6 background, were used as recipient mice for adoptive transfer experiments.

Next, 0.3 pmol of each of the three PCR fragments was mixed selleck compound with the primers (avc1758-1f and avc1758-2r; Table 1). The PCR conditions were as follows: after initial denaturation at 95°C for 2 mins, 30 cycles of denaturation at 95°C for 30 s, annealing at 40°C for 30 s, and extension at 72°C for 2 mins, followed by a final extension at 72°C for 3 mins. Next, the PCR fragments (avc1758-1::cat::avc1758-2 cassette) were precipitated with ethanol and dissolved in distilled water. 2 µg of PCR fragments was electroporated

into V. cholerae ATCC14033, which expresses λ Red recombinase from a temperature-sensitive plasmid, pKD46, to be integrated into the chromosome. The resultant 14033VC1758::cat was screened by spreading it onto LB agar containing Cm and 1 mg/mL L-arabinose at 37°C. Proteins in the culture supernatants were analyzed by SDS–PAGE and western blotting as described previously [18]. Anti-VopD2 antibodies were used to detect effector protein secretion. In all, 110 environmental and 14 clinical isolates were tested for the presence of T3SS-related genes using specific

PCR primers and 12 T3SS-positive strains were detected, including 10 environmental strains and 2 clinical isolates. No PCR fragments were amplified from the remaining 112 strains. The serogroups of the T3SS-positive isolates were determined and are listed in Table 2. Six serogroups were identified among nine of the strains, the details of which are as follows: O6 (three isolates), O12 (two isolates) and O39, O54, O84 and O103 (one isolate each). The other three strains formed rough colonies that could not be serogrouped (Table DAPT solubility dmso 2). PFGE genotyping showed that the 12 isolates had 10 different PFGE patterns (Fig. 1). There was one clonal cluster, which consisted of three isolates (EDL-070, DC-98022 and DC-98023). DC-98022 was selected for further analysis. The minimal similarity of the T3SS-related positive isolates was approximately 65%. No correlation was found between the PFGE cluster and serogroups. The T3SS-related

genes were distributed among V. cholerae strains that were diverse in serogroups and genotypes. To assess the similarity of T3SS-related gene clusters, PCR–RFLP Histamine H2 receptor analyses were performed. All PCR fragments from the 10 isolates with different PFGE profiles were amplified by RFLP-1 to -7 primer sets, except for RFLP-6 and -7 primer sets in the EB-0438 and EM-0772 strains. All PCR fragments with RFLP-1 and -5 primer sets had identical RFLP patterns. The other PCR fragments had similar RFLP patterns that differed by only a few bands (see Fig. S1(b) in the supporting information). Despite the diversity observed in PFGE profiles, the PCR-RFLP analyses of the T3SS-related gene region revealed comparatively similar patterns. The relatively conserved T3SS-related genes were distributed among diverse V. cholerae, which suggests horizontal transfer of T3SS-related genes. Because V.

Results were interpreted

as percent sensitive (%S), percent resistant (%R) and percent intermediate (%I) (Pardesi et al., 2007). Determination of the MIC required to inhibit the growth of six strains of A. baumannii using 14 antibiotics from different groups were carried out by an agar dilution method (Deshpande et al., 1993). Antibiotics were checked in the range of 1–1024 μg mL−1 (National Committee for Clinical Laboratory Standards, 2000). Plasmid isolation was done using the O’Sullivan and Klaenhammer method (O’Sullivan & Klaenhammer, 1993). Agarose gel electrophoresis was performed by 0.8% w/v agarose gel prepared in Tris-acetate selleck inhibitor buffer. Plasmid profiles were documented under UV light in gel documentation system (Alpha Innotech Corp.). Molecular weights of plasmids from different A. baumannii isolates were determined using the molecular weight determination parameter in gel documentation system MK-8669 purchase (Alpha Innotech Corp.). The plasmids from E. coli V517 (MTCC 131) were also included as the positive controls and used for

comparison to test plasmids as well as molecular weight determination (O’Sullivan & Klaenhammer, 1993). Multiple plasmid-containing A. baumannii strains (A1, A2 and A3) with biofilm formation ability were selected for plasmid curing using E. coli MTCC 131 as a standard control. Curing was performed by the use of different curing agents such as ethidium bromide, plumbagin, Montelukast Sodium acriflavin and acridine orange (Shakibaie et al., 1999). The percentage of curing efficiency was expressed as the number of colonies with cured phenotype per 200 tested colonies. The confirmation of cured clones was performed by agarose gel electrophoresis. The MIC of cured colonies was also tested for loss of resistance to antibiotics by an agar dilution method (Shakibaie et al., 1999; Cusumano et al., 2010). Conjugational gene transfer was performed from A. baumannii A3 pUPI 801–807 (Ar, Cur, Cir, Csr, Cpr, Nfr) to E. coli HB 101 (rifampicin-resistant

mutant) by the membrane filter technique (Chopade et al., 1985). The frequency of intergeneric conjugation was determined as the number of transconjugants obtained mL-1 on selective medium divided by total viable count of the recipient (Deshpande & Chopade, 1994). Natural transformation was performed using the plate assay (Ray & Nielsen, 2005). Acinetobacter baylyi 7054 trpE was used as the host for transformation experiments and plasmid DNA from A. baumannii A3 was prepared as the donor strain (O’Sullivan & Klaenhammer, 1993). The experiments were carried out using plasmids: pUPI 801–807 (Ar, Cur, Cir, Csr, Cpr, Nfr) from A. baumannii A3 and competent cells of A. baylyi 7054 trpE as the recipient. They were confirmed for the presence of transferred plasmids according to O’Sullivan & Klaenhammer (1993).

We believe that prolonged ischemia time and hypothermia precipitated erythrocyte sickling within the flap, causing intra-flap thrombosis that propagated to the pedicle. While sickle cell diseases are not a contraindication to free tissue transfer, we believe that flap cooling should be utilized with

caution in this circumstance. © 2012 Wiley Periodicals, Inc. “
“Surgical procedure of great toe wrap-around flap combined with second toe medial flap free transfer Z-VAD-FMK purchase for reconstructing completely degloved fingers was introduced. The treatment outcomes were evaluated. 10 fingers in 7 cases were involved in this series. The great toe wrap-around flap with dorsalis pedis skin covered the dorsal and most palmar side of the injured finger. The second toe medial flap covered the proximal palmar portion of the finger. The combined flap was revascularized

with nerve repair. Rehabilitation started Maraviroc molecular weight two weeks postoperatively. All flaps survived except one was partial failure due to distal phalange necrosis. Recipient areas achieved primary wound healing in 9 fingers. Skin graft at donor site achieved primary survival except delayed healing in one case. All patients were followed-up from 34 to 76 months. The appearance of reconstructed fingers was satisfactory. Nail growth well except that one nail was the atrophic and another was defect. Range of active motion in the metacarpophalangeal joint was from 60° to 80° and the proximal interphalange joint was 40° to 70°. Two-point discrimination was between 8 mm and 12 mm. All patients walked with no interference. There was no pain and no swelling at donor site. According to the results, this procedure is recommended to reconstruct total degolving finger which has intact phalanges and tendons. © 2010 Wiley-Liss, Inc. Microsurgery 30:449–456, 2010. “
“Complete circumferential degloving injury of the digits usually results in a large cutaneous defect with tendinous structure and bone and joint exposure. When revascularization is not possible, a thin and adequately sized flap is required to resurface the defect, restore finger function,

and prevent amputation. In this report, we present our experience Clomifene with reconstruction of the entire circumferential degloving injury of the digits using free fasciocutaneous flaps. Between February 2006 and January 2011, 9 male patients with circumferential degloving injury of 9 digits underwent reconstruction using free fasciocutaneous flap transfer with the posterior interosseous artery flap, medial sural artery flap, anteromedial thigh flap, or radial forearm flap. The average flap size was 14.2 × 6.9 cm. Donor sites were closed primarily or covered with split-thickness skin graft. All flaps survived completely and the donor sites healed without complications. The mean follow-up period was 34.8 months. A maximum Kapandji score (10/10) was seen in 2 cases with crushed thumbs.

For example, Th17-cell priming requirements have elicited disputes, primarily due to inconsistencies between mouse and human cytokine requirements and in particular due to the controversial role of TGF-β in Th17-cell differentiation [65]. Although Th-cell polarization is a multilayered process that is dependent on signal strength and

the engagement of different co-stimulatory molecules following antigen processing, and the establishment of a complex immunological synapse, the focus of interest has been on cytokine requirements. Most of the approaches to dissect Th17 priming conditions have therefore used polyclonal stimulation of naïve buy RG7204 T cells with anti-CD3 and anti-CD28 antibodies in the presence of well-defined cytokine combinations in vitro. However, human Th17-cell polarization following antigen-specific stimulation with microbes has recently revealed that priming requirements differ, depending on microbial antigen BI 6727 cell line specificity even within the same class of Th cells [12]. Microbial ligands that generate Th17-cell responses through TLR and CLR signaling have primarily, although not exclusively, been defined for C. albicans [66, 67]. Fungal components have been shown to bind to

Dectin1, Dectin2, and Mincle expressed on APCs, which leads to the recruitment of the tyrosine kinase Syk, activation of the adaptor CARD9, and finally to secretion of IL-23, IL-1, IL-6 [66, 67], which are involved in the generation of human Th17 cells. Interestingly, the generation of C. albicans-specific human Th17 cells has been shown to be highly dependent on IL-1β, while S. aureus-specific Th17 cells can be primed in its absence [12]. This not only indicates different pathways for the generation of human Th17 cells but also a strong link between microbial antigen specificities of Th cells with their respective priming requirements.

This has important consequences for the functionality of Th17 cells, since C. albicans-specific, and thus IL-1β-dependent Th17 cells have been shown to co-express IL-17 and IFN-γ but not IL-10, while S. aureus-specific Th17 cells have been shown to be IFN-γ negative but IL-10 positive [12]. IL-1β therefore acts as a molecular switch factor for the generation of pro- versus anti-inflammatory Galactosylceramidase Th17-cell properties [3, 68]. A model disease to exemplify the two-sided interactions of environment and Th cells is chronic mucocutaneous candidiasis, a rare disease characterized by chronic and persistent infection of skin and mucosa with Candida species [69]. Numerous mutations affecting the differentiation and function of Th17 cells have been described for chronic mucocutaneous candidiasis. Namely, humans with loss-of-function mutations in CARD9 and STAT3 or gain-of-function mutations in STAT1 have reduced Th17 cells [70-72]. In other families, IL-17 or its receptor is mutated, or autoantibodies against IL-17 are secreted [73, 74].

This threshold could be numerical or physiological, CH5424802 nmr or a combination of both. It therefore takes a “team effort” to cause periodontitis in that the disease requires cooperative

interactions among bacteria with different roles. A recently formulated model that accommodates these concepts is called the polymicrobial synergy and dysbiosis (PSD) model [2]. This model holds that physiologically compatible organisms assemble into heterotypic communities, which exist in a controlled immunoinflammatory state. While they are pro-inflammatory and can produce toxic products such as proteases, overgrowth and overt pathogenicity are controlled by the host response. The microbial constituents of the communities can vary among individuals, among sites, and over time. Colonization by keystone pathogens such as P.

gingivalis elevates the virulence of the entire community following interactive communication with accessory pathogens. Initially, host immune surveillance is impaired and the dysbiotic community increases in number. Subsequently, the community proactively induces inflammation to sustain itself with derived nutrients, which will also shape a modified “inflammophilic” community. The action of pathobionts in the community, in addition to overt pathogens, eventually leads to destruction of periodontal tissues. The PSD model reconciles a number of features of periodontal Selleck Lenvatinib disease that were discordant with earlier concepts of pathogenicity. These include: the variable microbiota at disease sites, even within the same patient; the presence of pathogens

in the absence of disease; the episodic nature of the disease; and the failure of P. gingivalis to cause periodontitis in the absence of the commensal microbiota [13]. Bacteria on human mucosal surfaces tend to accumulate into complex multispecies communities, a process controlled by a sophisticated series of interbacterial signaling and host response interactions. Within these communities, bacteria have specialized roles, such as provision of an essential enzyme for progressive nutrient metabolism. Bacteria tuclazepam that influence the pathogenicity of the entire community are keystone pathogens, the best-documented example of which is P. gingivalis. While P. gingivalis can affect gene and protein expression in other community members, the major keystone-related influence of the organism is likely through interference with host immunity. This is accomplished by a multipronged approach that compromises immune function on a number of levels (Fig. 1 and 3). It is important to bear in mind, however, that periodontitis is an inflammatory disease, and thus the timing, location, and context of immune suppression by P. gingivalis will have major significance for the ultimate progression of disease.