XX sex chromosome complement modulates immune responses to heat-killed Streptococcus pneumoniae immunization in a microbiome-dependent manner.

BACKGROUND: Differences in male vs. female immune responses are well-documented and have significant clinical implications. While the immunomodulatory effects of sex hormones are well established, the contributions of sex chromosome complement (XX vs. XY) and gut microbiome diversity on immune sexual dimorphisms have only recently become appreciated. Here we investigate the individual and collaborative influences of sex chromosome complements and gut microbiota on humoral immune activation. METHODS: Male and female Four Core Genotype (FCG) mice were immunized with heat-killed Streptococcus pneumoniae (HKSP). Humoral immune responses were assessed, and X-linked immune-related gene expression was evaluated to explain the identified XX-dependent phenotype. The functional role of Kdm6a, an X-linked epigenetic regulatory gene of interest, was evaluated ex vivo using mitogen stimulation of B cells. Additional influences of the gut microbiome on sex chromosome-dependent B cell activation was also evaluated by antibiotically depleting gut microbiota prior to HKSP immunization. Reconstitution of the depleted microbiome with short-chain fatty acid (SCFA)-producing bacteria tested the impact of SCFAs on XX-dependent immune activation. RESULTS: XX mice exhibited higher HKSP-specific IgM-secreting B cells and plasma cell frequencies than XY mice, regardless of gonadal sex. Although Kdm6a was identified as an X-linked gene overexpressed in XX B cells, inhibition of its enzymatic activity did not affect mitogen-induced plasma cell differentiation or antibody production in a sex chromosome-dependent manner ex vivo. Enhanced humoral responses in XX vs. XY immunized FCG mice were eliminated after microbiome depletion, indicating that the microbiome contributes to the identified XX-dependent immune enhancement. Reconstituting microbiota-depleted mice with select SCFA-producing bacteria enhanced fecal SCFA concentrations and increased humoral responses in XX, but not XY, FCG mice. However, exposure to the SCFA propionate alone did not enhance mitogenic B cell stimulation in ex vivo studies. CONCLUSIONS: FCG mice have been used to assess sex hormone and sex chromosome complement influences on various sexually dimorphic traits. The current study indicates that the gut microbiome impacts humoral responses in an XX-dependent manner, suggesting that the collaborative influence of gut bacteria and other sex-specific factors should be considered when interpreting data aimed at delineating the mechanisms that promote sexual dimorphism.

Male and female immune systems differ in their ability to respond to infectious challenge. While males tend to be more susceptible to infection and produce lower amounts of antibodies in response to vaccination, females are more prone to develop autoimmune and inflammatory diseases. Key contributors to these differences include sex hormones, sex chromosome complement (XX in females vs. XY in males), and distinct gut microbial communities capable of regulating immune activation. While each factor has been studied individually, this research underscores the potential for these factors to collaboratively impact immune activation. Here, possession of an XX vs. XY sex chromosome complement was demonstrated to enhance antibody responses to heat-killed Streptococcus pneumoniae vaccination. While attempting to determine the underlying cause of this immune enhancement, the gut microbiome was identified to play a critical role. In the absence of an intact gut microbiome, XX immune activation was reduced to levels similar to those seen in XY sex chromosome complement-possessing mice. Replacement of the depleted gut microbiomes with select SCFA-producing bacterial species enhanced SCFA levels in antibiotic-treated mice and rescued the XX-dependent immune enhancement, suggesting a SCFA-mediated contribution. Further studies are needed to determine exactly how these select bacteria impact immune activation in a sex chromosome complement-dependent manner. Our findings highlight the need to consider the collaborative effects of individual sex-specific factors when attempting to understand immune sex biases, as a better understanding of these interactions will likely pave the way for improving therapeutics and vaccines tailored to both sexes.

XX sex chromosome complement modulates immune responses to heat-killed Streptococcus pneumoniae immunization in a microbiome-dependent manner.

Background: Differences in male vs. female immune responses are well-documented and have significant clinical implications. While the immunomodulatory effects of sex hormones are well established, the contributions of sex chromosome complement (XX vs. XY) and gut microbiome diversity on immune sexual dimorphisms have only recently become appreciated. Here we investigate the individual and collaborative influences of sex chromosome complements and gut microbiome bacteria on humoral immune activation. Methods: Sham-operated and gonadectomized male and female Four Core Genotype (FCG) mice were immunized with heat-killed Streptococcus pneumoniae (HKSP). Humoral immune responses were assessed, and X-linked immune-related gene expression was evaluated to explain the identified XX-dependent phenotypes. Ex vivo studies investigated the functional role of Kdm6a, an X-linked epigenetic regulatory gene of interest, in mitogenic B cell activation. Additionally, we examined whether gut microbiome communities, or their metabolites, differentially influence immune cell activation in a sex chromosome-dependent manner. Endogenous gut microbiomes were antibiotically depleted and reconstituted with select short-chain fatty acid (SCFA)-producing bacteria prior to HKSP immunization and immune responses assessed. Results: XX mice exhibited higher HKSP-specific IgM-secreting B cells and plasma cell frequencies than XY mice, regardless of gonadal sex. Although Kdm6a was identified as an X-linked gene overexpressed in XX B cells, inhibition of its enzymatic activity did not affect mitogen-induced plasma cell differentiation or antibody production in a sex chromosome-dependent manner ex vivo. Enhanced humoral responses in XX vs. XY immunized FCG mice were eliminated after microbiome depletion, indicating that the microbiome contributes to the identified XX-dependent immune enhancement. Reconstituting microbiota-depleted mice with select SCFA-producing bacteria increased humoral responses in XX, but not XY, FCG mice. This XX-dependent enhancement appears to be independent of SCFA production in males, while female XX-dependent responses relied on SCFAs. Conclusions: FCG mice have been used to assess the influence of sex hormones and sex chromosome complements on various sexually dimorphic traits. The current study indicates that the gut microbiome impacts humoral responses in an XX-dependent manner, suggesting that the collaborative influence of gut bacteria and other sex-specific factors should be considered when interpreting data aimed at delineating the mechanisms that promote sexual dimorphism.

Evaluating Macrophages in Immunotoxicity Testing.

Macrophages are a heterogeneous group of cells that have a multitude of functions depending on their differentiation state. While classically known for their phagocytic and antigen presentation abilities, it is now evident that these cells fulfill homeostatic functions beyond the elimination of invading pathogens. In addition, macrophages have also been implicated in the downregulation of inflammatory responses following pathogen removal, tissue remodeling, repair, and angiogenesis. Alterations in macrophage differentiation and/or activity due to xenobiotic exposure can have grave consequences on organismal homeostasis, potentially contributing to disease due to immunosuppression or chronic inflammatory responses, depending upon the pathways affected. In this chapter, we provide an overview of the macrophages subtypes, their origin and a general discussion of several different assays used to assess their functional status.

The XX Sex Chromosome Complement is Required in Male and Female Mice for Enhancement of Immunity Induced by Exposure to 3,4-Dichloropropionanilide.

PROBLEM: The chemical propanil enhances antibody responses to a heat-killed Streptococcus pneumoniae (HKSP) vaccine. The enhanced response is dependent on gonads in females, but independent of gonads in males. The sex differences in the immune response may be due to sexual differentiation of the immune system or sex chromosome complement. METHOD OF STUDY: To test the hypothesis that the immune system is sexually differentiated, newborn C57BL/6 pups were treated with testosterone propionate (TP) or placebo. The role of sex chromosome complement was investigated using the 4-core genotypes (FCG) model of XXF and XYF gonadal females (ovaries), and XXM and XYM gonadal males (testes). For some experiments, mice were gonadectomized or sham gonadectomized. All mice were vaccinated with HKSP, treated with propanil, and the antibody response determined at day seven. RESULTS: Neonatal TP did not alter the response to HKSP. In FCG mice, propanil significantly enhanced the immune response in XXF females and XXM males, but not in XYF females or XYM males. CONCLUSION: The immune system of females was not masculinized by neonatal TP treatment. Sex chromosome complement significantly contributes to the sexually dimorphic immune response after propanil exposure.

Expression kinetics of miRNA involved in dermal toluene 2,4-diisocyanate sensitization.

Allergic disease is an important occupational health concern, with work-related asthma and allergic contact dermatitis being the most frequently diagnosed occupational illnesses. Diisocyanates, particularly toluene 2,4-diisocyanate (TDI), have been the leading cause of occupational asthma for many years. Understanding the mechanisms behind allergic disease is critical for treatment and prevention. Recently, the study of post-transcriptional regulation by microRNAs (miRNA) has shed light on mechanisms of allergic disease. The present studies report the expression of miRNA during the sensitization phase of an allergic response to TDI in a murine model. Female BALB/c mice were dermally exposed to TDI (0.1-15% [v/v]) or vehicle. RNA was isolated from superficial parotid lymph nodes at timepoints between 1 h and 15 days post-exposure and then miRNA expression was analyzed using array and real-time quantitative PCR analysis. Consistent changes in miRNA expression were identified for miR-21, miR-22, miR-27b, miR-31, miR-126, miR-155, miR-210, and miR-301a. Following TDI exposure, peak expression was observed by Day 4 for the majority of miRNA evaluated with trends in expression correlated to exposure concentration. Confirmed and predicted targets were identified using Diana-microT, miRanda, miRwalk, and Targetscan algorithms. Evaluation of mRNA expression of cytokine and transcription factor targets suggests that miRNA may have a central role early in TDI sensitization. Understanding the role of these miRNA and their specific mechanism of action in sensitization to TDI may provide pertinent information for the identification of other chemical sensitizers while also contributing to the treatment and prevention of allergic disease.

Evaluation of the hypersensitivity potential of alternative butter flavorings.

Concern has been raised over the association of diacetyl with lung disease clinically resembling bronchiolitis obliterans in food manufacturing workers. This has resulted in the need for identification of alternative chemicals to be used in the manufacturing process. Structurally similar chemicals, 2,3-pentanedione, 2,3-hexanedione, 3,4-hexanedione and 2,3-heptanedione, used as constituents of synthetic flavoring agents have been suggested as potential alternatives for diacetyl, however, immunotoxicity data on these chemicals are limited. The present study evaluated the dermal irritation and sensitization potential of diacetyl alternatives using a murine model. None of the chemicals were identified as dermal irritants when tested at concentrations up to 50%. Similar to diacetyl (EC3=17.9%), concentration-dependent increases in lymphocyte proliferation were observed following exposure to all four chemicals, with calculated EC3 values of 15.4% (2,3-pentanedione), 18.2% (2,3-hexanedione), 15.5% (3,4-hexanedione) and 14.1% (2,3-heptanedione). No biologically significant elevations in local or total serum IgE were identified after exposure to 25-50% concentrations of these chemicals. These results demonstrate the potential for development of hypersensitivity responses to these proposed alternative butter flavorings and raise concern about the use of structurally similar replacement chemicals. Additionally, a contaminant with strong sensitization potential was found in varying concentrations in diacetyl obtained from different producers.

Immunotoxicity and allergic potential induced by topical application of dimethyl carbonate (DMC) in a murine model.

Dimethyl carbonate (DMC) is an industrial chemical, used as a paint and adhesive solvent, with the potential for significant increases in production. Using select immune function assays, the purpose of these studies was to evaluate the immunotoxicity of DMC following dermal exposure using a murine model. Following a 28-day exposure, DMC produced a significant decrease in thymus weight at concentrations of 75% and greater. No effects on body weight, hematological parameters (erythrocytes, leukocytes, and their differentials), or immune cell phenotyping (B-cells, T-cells, and T-cell sub-sets) were identified. The IgM antibody response to sheep red blood cell (SRBC) was significantly reduced in the spleen but not the serum. DMC was not identified to be an irritant and evaluation of the sensitization potential, conducted using the local lymph node assay (LLNA) at concentrations ranging from 50-100%, did not identify increases in lymphocyte proliferation. These results demonstrate that dermal exposure to DMC induces immune suppression in a murine model and raise concern about potential human exposure and the need for occupational exposure regulations.

Exposure to triclosan augments the allergic response to ovalbumin in a mouse model of asthma.

During the last decade, there has been a remarkable and unexplained increase in the prevalence of asthma. These studies were conducted to investigate the role of dermal exposure to triclosan, an endocrine-disrupting compound, on the hypersensitivity response to ovalbumin (OVA) in a murine model of asthma. Triclosan has had widespread use in the general population as an antibacterial and antifungal agent and is commonly found in consumer products such as soaps, deodorants, toothpastes, shaving creams, mouthwashes, and cleaning supplies. For these studies, BALB/c mice were exposed dermally to concentrations of triclosan ranging from 0.75 to 3% (0.375-1.5mg/mouse/day) for 28 consecutive days. Concordantly, mice were ip injected with OVA (0.9 µg) and aluminum hydroxide (0.5mg) on days 1 and 10 and challenged with OVA (125 µg) by pharyngeal aspiration on days 19 and 27. Compared with the animals exposed to OVA alone, increased spleen weights, OVA-specific IgE, interleukin-13 cytokine levels, and numbers of lung eosinophils were demonstrated when mice were coexposed to OVA and triclosan. Statistically significant increases in OVA-specific and nonspecific airway hyperreactivity were observed for all triclosan coexposed groups compared with the vehicle and OVA controls. In these studies, exposure to triclosan alone was not demonstrated to be allergenic; however, coexposure with a known allergen resulted in enhancement of the hypersensitivity response to that allergen, suggesting that triclosan exposure may augment the allergic responses to other environmental allergens.

Immunotoxicology: fifty years of global scientific progress.

The Immunotoxicology Specialty Section of the Society of Toxicology (SOT) celebrated the 50(th) Anniversary of the SOT by constructing a poster to highlight the milestones of Immunotoxicology during that half-century period. This poster was assembled by an ad hoc committee and intertwines in words, citations, graphics, and photographs our attempts to capture a timeline reference of the development and progressive movement of immunotoxicology across the globe. This poster was displayed during the 50(th) Annual SOT Meeting in Washington DC in March, 2011. The poster can be accessed by any Reader at the SOT Website via the link http://www.toxicology.org/AI/MEET/AM2011/posters_rcsigss.asp#imss. We dedicate this poster to all of the founders and the scientists that followed them who have made the discipline of Immunotoxicology what it is today.

Irritancy and allergic responses induced by exposure to the indoor air chemical 4-oxopentanal.

Over the last two decades, there has been an increasing awareness regarding the potential impact of indoor air pollution on human health. People working in an indoor environment often experience symptoms such as eye, nose, and throat irritation. Investigations into these complaints have ascribed the effects, in part, to compounds emitted from building materials, cleaning/consumer products, and indoor chemistry. One suspect indoor air contaminant that has been identified is the dicarbonyl 4-oxopentanal (4-OPA). 4-OPA is generated through the ozonolysis of squalene and several high-volume production compounds that are commonly found indoors. Following preliminary workplace sampling that identified the presence of 4-OPA, these studies examined the inflammatory and allergic responses to 4-OPA following both dermal and pulmonary exposure using a murine model. 4-OPA was tested in a combined local lymph node assay and identified to be an irritant and sensitizer. A Th1-mediated hypersensitivity response was supported by a positive response in the mouse ear swelling test. Pulmonary exposure to 4-OPA caused a significant elevation in nonspecific airway hyperreactivity, increased numbers of lung-associated lymphocytes and neutrophils, and increased interferon-γ production by lung-associated lymph nodes. These results suggest that both dermal and pulmonary exposure to 4-OPA may elicit irritant and allergic responses and may help to explain some of the adverse health effects associated with poor indoor air quality.

Evaluation of furfuryl alcohol sensitization potential following dermal and pulmonary exposure: enhancement of airway responsiveness.

Furfuryl alcohol is considered by the U.S. Environmental Protection Agency to be a high volume production chemical, with over 1 million pounds produced annually. Due to its high production volume and its numerous industrial and consumer uses, there is considerable potential for work-related exposure, as well as exposure to the general population, through pulmonary, oral, and dermal routes of exposure. Human exposure data report a high incidence of asthma in foundry mold workers exposed to furan resins, suggesting potential immunologic effects. Although furfuryl alcohol was nominated and evaluated for its carcinogenic potential by the National Toxicology Program, studies evaluating its immunotoxicity are lacking. The studies presented here evaluated the immunotoxic potential of furfuryl alcohol following exposure by the dermal and pulmonary routes using a murine model. When tested in a combined irritancy local lymph node assay, furfuryl alcohol was identified to be an irritant and mild sensitizer (EC3 = 25.6%). Pulmonary exposure to 2% furfuryl alcohol resulted in enhanced airway hyperreactivity, eosinophilic infiltration into the lungs, and enhanced cytokine production (IL-4, IL-5, and interferon-γ) by ex vivo stimulated lung-associated draining lymphoid cells. Airway hyperreactivity and eosinophilic lung infiltration were augmented by prior dermal exposure to furfuryl alcohol. These results suggest that furfuryl alcohol may play a role in the development of allergic airway disease and encourage the need for additional investigation.

Dermal penetration potential of perfluorooctanoic acid (PFOA) in human and mouse skin.

Recent data, using a murine model, have indicated that dermal exposure to perfluorooctanoic acid (PFOA) induces immune modulation, suggesting that this may be an important route of PFOA exposure. To investigate the dermal penetration potential of PFOA, serum concentrations were analyzed in mice following topical application. Statistically significant and dose-responsive increases in serum PFOA concentrations were identified. In vitro dermal penetration studies also demonstrated that PFOA permeates both mouse and human skin. Investigation into the mechanisms mediating PFOA penetration demonstrated that dermal absorption was strongly dependent upon the ionization status of PFOA. In addition, PFOA solid, but not 1% PFOA/acetone solution, was identified as corrosive using a cultured epidermis in vitro model. Despite its corrosive potential, expression of inflammatory cytokines in the skin of topically exposed mice was not altered. These data suggest that PFOA is dermally absorbed and that under certain conditions the skin may be a significant route of exposure.

Potential immunotoxicological health effects following exposure to COREXIT 9500A during cleanup of the Deepwater Horizon oil spill.

Workers involved in the Deepwater Horizon oil spill cleanup efforts reported acute pulmonary and dermatological adverse health effects. These studies were undertaken to assess the immunotoxicity of COREXIT 9500A, the primary dispersant used in cleanup efforts, as a potential causative agent. COREXIT 9500A and one of its active ingredients, dioctyl sodium sulfosuccinate (DSS), were evaluated using murine models for hypersensitivity and immune suppression, including the local lymph node assay (LLNA), phenotypic analysis of draining lymph node cells (DLN), mouse ear swelling test (MEST), total serum immunoglobulin E (IgE), and the plaque-forming cell (PFC) assay. Dermal exposure to COREXIT 9500A and DSS induced dose-responsive increases in dermal irritation and lymphocyte proliferation. The EC3 values for COREXIT 9500A and DSS were 0.4% and 3.9%, respectively, resulting in a classification of COREXIT 9500A as a potent sensitizer and DSS as a moderate sensitizer. A T-cell-mediated mechanism underlying the LLNA was supported by positive responses in the MEST assay for COREXIT and DSS, indicated by a significant increase in ear swelling 48 h post challenge. There were no marked alterations in total serum IgE or B220+/IgE+ lymph-node cell populations following exposure to COREXIT 9500A. Significant elevations in interferon (IFN)-γ but not interleukin (IL)-4 protein were also observed in stimulated lymph node cells. The absence of increases in IgE and IL-4 in the presence of enhanced lymphocyte proliferation, positive MEST responses, and elevations in IFN-γ suggest a T-cell-mediated mechanism. COREXIT 9500A did not induce immunosuppression in the murine model.

Allergic Potential and Immunotoxicity Induced by Topical Application of 1-Chloro-4-(Trifluoromethyl)Benzene (PCBTF) in a Murine Model.

The purpose of the studies in this paper was to evaluate the allergic potential, immunotoxicity, and irritancy of the occupationally relevant chemical, 1-chloro-4-(trifluoromethyl)benzene, also known as parachlorobenzotrifluoride (PCBTF), following dermal exposure in a murine model. Evaluation of the sensitization potential, conducted using the local lymph node assay (LLNA) at concentrations ranging from 50% to 100%, identified a dose-dependent increase in lymphocyte proliferation with a calculated EC3 value of 53.1%. While no elevations in total or specific IgE were observed after exposure to any concentration of the chemical, significant increases in IFN-γ protein production by stimulated draining lymphoid cells were observed, indicating a T-cell-mediated response. Dermal exposure to PCBTF was not found to alter the immune response to a T-cell-dependant antigen. These results demonstrate that PCBTF has the potential to induce allergic sensitization following dermal exposure and based on LLNA results would be classified as a weak sensitizer.

Evaluation of dicarbonyls generated in a simulated indoor air environment using an in vitro exposure system.

Over the last two decades, there has been increasing awareness regarding the potential impact of indoor air pollution on health. Exposure to volatile organic compounds (VOCs) or oxygenated organic compounds formed from indoor chemistry has been suggested to contribute to adverse health effects. These studies use an in vitro monitoring system called VitroCell, to assess chemicals found in the indoor air environment. The structurally similar dicarbonyls diacetyl, 4-oxopentanal (4-OPA), glyoxal, glutaraldehyde, and methyl glyoxal were selected for use in this system. The VitroCell module was used to determine whether these dicarbonyls were capable of inducing inflammatory cytokine expression by exposed pulmonary epithelial cells (A549). Increases in the relative fold change in messenger RNA expression of the inflammatory mediators, interleukin (IL)-6, IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor alpha (TNF-alpha) were identified following exposure to diacetyl, 4-OPA, glyoxal, glutaraldehyde, and methyl glyoxal when compared to a clean air control. Consistent results were observed when the protein levels of these cytokines were analyzed. Exposure to 4-OPA significantly elevated IL-8, IL-6, GM-CSF, and TNF-alpha while glutaraldehyde caused significant elevations in IL-6, IL-8, and TNF-alpha. IL-6 and IL-8 were also significantly elevated after exposure to diacetyl, glyoxal, and methyl glyoxal. These studies suggest that exposure to structurally similar oxygenated reaction products may be contributing to some of the health effects associated with indoor environments and may provide an in vitro method for identification and characterization of these potential hazards.

Irritancy and allergic responses induced by topical application of ortho-phthalaldehyde.

Although ortho-phthalaldehyde (OPA) has been suggested as an alternative to glutaraldehyde for the sterilization and disinfection of hospital equipment, the toxicity has not been thoroughly investigated. The purpose of these studies was to evaluate the irritancy and sensitization potential of OPA. The EpiDerm Skin Irritation Test was used to evaluate in vitro irritancy potential of OPA and glutaraldehyde. Treatment with 0.4125 and 0.55% OPA induced irritation, while glutaraldehyde exposure at these concentrations did not. Consistent with the in vitro results, OPA induced irritancy, evaluated by ear swelling, when mice were treated with 0.75%. Initial evaluation of the sensitization potential was conducted using the local lymph node assay at concentrations ranging from 0.005 to 0.75%. A concentration-dependent increase in lymphocyte proliferation was observed with a calculated EC3 value of 0.051% compared to that of 0.089%, previously determined for glutaraldehyde. Immunoglobulin (Ig) E-inducing potential was evaluated by phenotypic analysis of draining lymph node (DLN) cells and measurement of total and specific serum IgE levels. The 0.1 and 0.75% exposed groups yielded significant increases in the IgE+B220+ cell population in the lymph nodes while the 0.75% treated group demonstrated significant increases in total IgE, OPA-specific IgE, and OPA-specific IgG(1). In addition, significant increases in interleukin-4 messenger RNA and protein expression in the DLNs were observed in OPA-treated groups. The results demonstrate the dermal irritancy and allergic potential of OPA and raise concern about the proposed/intended use of OPA as a safe alternative to glutaraldehyde.

Mycobacterium tuberculosis cell wall glycolipids directly inhibit CD4+ T-cell activation by interfering with proximal T-cell-receptor signaling.

Immune evasion is required for Mycobacterium tuberculosis to survive in the face of robust adaptive CD4(+) T-cell responses. We have previously shown that M. tuberculosis can indirectly inhibit CD4(+) T cells by suppressing the major histocompatibility complex class II antigen-presenting cell function of macrophages. This study was undertaken to determine if M. tuberculosis could directly inhibit CD4(+) T-cell activation. Murine CD4(+) T cells were purified from spleens by negative immunoaffinity selection followed by flow sorting. Purified CD4(+) T cells were activated for 16 to 48 h with CD3 and CD28 monoclonal antibodies in the presence or absence of M. tuberculosis and its subcellular fractions. CD4(+) T-cell activation was measured by interleukin 2 production, proliferation, and expression of activation markers, all of which were decreased in the presence of M. tuberculosis. Fractionation identified that M. tuberculosis cell wall glycolipids, specifically, phosphatidylinositol mannoside and mannose-capped lipoarabinomannan, were potent inhibitors. Glycolipid-mediated inhibition was not dependent on Toll-like receptor signaling and could be bypassed through stimulation with phorbol 12-myristate 13-acetate and ionomycin. ZAP-70 phosphorylation was decreased in the presence of M. tuberculosis glycolipids, indicating that M. tuberculosis glycolipids directly inhibited CD4(+) T-cell activation by interfering with proximal T-cell-receptor signaling.

Antigen-independent adhesion and cell spreading by inducible costimulator engagement inhibits T cell migration in a PI-3K-dependent manner.

Engagement of the costimulatory protein ICOS activates effector/memory T cells in tissue by enhancing TCR-mediated proliferation and cytokine production. We now report that in an antigen-independent manner, ICOS also induces adhesion and spreading in human effector/memory T cells, consequently inhibiting cell migration. T cell spreading and elongation after ICOS ligation are accompanied by the formation of two types of actin-rich membrane protrusions: thin, finger-like structures similar to filopodia and short, discrete microspikes. Although filopodia/microspike formation occurs independently of the PI-3K signaling cascade, ICOS-mediated T cell elongation depends on PI-3K activity, which inhibits the accumulation of GTP-bound RhoA. Further inhibition of RhoA activation exacerbates the ICOS-mediated, elongated phenotype. We propose that in inflamed tissue, ICOS engagement by ICOS ligand on a professional or nonprofessional APC prevents the forward motility of the T cell by inhibiting RhoA-dependent uropod retraction. The resulting ICOS-induced T cell spreading and filopodia/microspike formation may promote antigen recognition by enhancing a T cell's scanning potential of an adherent APC surface.

Haemophilus influenzae type b-outer membrane protein complex glycoconjugate vaccine induces cytokine production by engaging human toll-like receptor 2 (TLR2) and requires the presence of TLR2 for optimal immunogenicity.

Conjugate vaccines consisting of the capsular polysaccharide (PS) of Haemophilus influenzae type b (Hib) covalently linked to carrier proteins, unlike pure PS, are immunogenic in infants and have significantly reduced Hib infections in the United States, but require multiple doses to induce protective anti-PS Ab titers. Hib-meningococcal outer membrane protein complex (OMPC) conjugate vaccine, however, elicits protective anti-PS Ab titers after one dose. We found that OMPC and Hib-OMPC engaged human Toll-like receptor 2 (TLR2) expressed in human embryonic kidney (HEK) cells, inducing IL-8 production, and engaged mouse TLR2 on bone marrow-derived dendritic cells, inducing TNF release. Hib conjugated to the carrier proteins CRM(197) and tetanus toxoid did not engage TLR2 on HEK or dendritic cells. Engagement of TLR2 by Hib-OMPC was MyD88 dependent, as Hib-OMPC-induced TNF production was ablated in MyD88 knockout (KO) mice. Hib-OMPC was significantly less immunogenic in TLR2 KO mice, inducing lower Hib PS IgG and IgM titers compared with those in wild-type mice. Splenocytes from OMPC-immunized TLR2 KO mice also produced significantly less IL-6 and TNF-alpha than those from wild-type mice. Hib-OMPC is unique among glycoconjugate vaccines by engaging TLR2, and the ability of Hib-OMPC to elicit protective levels of Abs after one dose may be related to TLR2-mediated induction and regulation of cytokines produced by T cells and macrophages in addition to the peptide/MHC II-dependent recruitment of T cell help commonly afforded by carrier proteins. TLR2 engagement by an adjuvant or carrier protein may be a useful strategy for augmentation of the anti-PS Ab response induced by glycoconjugate vaccines.

Genetic variation at the mitochondrial large-subunit rRNA locus of Pneumocystis isolates from simian immunodeficiency virus-infected rhesus macaques.

The nucleotide sequences of a segment of the Pneumocystis mitochondrial large-subunit (mt LSU) rRNA gene from rhesus macaques coinfected with simian immunodeficiency virus (SIV) and Pneumocystis carinii were examined. Of 12 isolates examined, 3 were found to be identical and the others showed substantial sequence variation, with up to 13% divergence among variants. We identified two general sequence types that differed at several sites, including a conserved 26-nucleotide insertion. Four monkeys had evidence of two Pneumocystis variants present simultaneously, indicative of a mixed infection. There was a high degree of variance between the rhesus macaque-derived Pneumocystis mt LSU rRNA gene sequence and the cognate sequences in Pneumocystis organisms derived from other hosts. Analysis of the mt LSU rRNA genes of Pneumocystis organisms derived from rhesus macaques and several other mammalian hosts supports the observation that rhesus macaque-derived Pneumocystis is most closely related to human-derived PNEUMOCYSTIS: In addition, the data identify the mt LSU rRNA gene as an informative locus for transmission and epidemiological studies of the SIV-rhesus macaque model of Pneumocystis infection.