Sequential production of IL-2, IFN-gamma and IL-10 by individual staphylococcal enterotoxin B-activated T helper lymphocytes

Plasticity and lineage commitment of individual TH1 cells are determined by stable T-bet expression quantities

T helper 1 (TH1) cell identity is defined by the expression of the lineage-specifying transcription factor T-bet. Here, we examine the influence of T-bet expression heterogeneity on subset plasticity by leveraging cell sorting of distinct in vivo-differentiated TH1 cells based on their quantitative expression of T-bet and interferon-γ. Heterogeneous T-bet expression states were regulated by virus-induced type I interferons and were stably maintained even after secondary viral infection. Exposed to alternative differentiation signals, the sorted subpopulations exhibited graded levels of plasticity, particularly toward the TH2 lineage: T-bet quantities were inversely correlated with the ability to express the TH2 lineage-specifying transcription factor GATA-3 and TH2 cytokines. Reprogramed TH1 cells acquired graded mixed TH1 + TH2 phenotypes with a hybrid epigenetic landscape. Continuous presence of T-bet in differentiated TH1 cells was essential to ensure TH1 cell stability. Thus, innate cytokine signals regulate TH1 cell plasticity via an individual cell-intrinsic rheostat to enable T cell subset adaptation to subsequent challenges.

IL-10 revisited in systemic lupus erythematosus

IL-10 is a cytokine with pleiotropic functions, particularly known for its suppressive effects on various immune cells. Consequently, it can limit the pathogenesis of inflammatory diseases, such as multiple sclerosis (MS), inflammatory bowel disease, Crohn’s disease, and Epidermolysis bullosa acquisita, among others. Recent evidence however indicates that it plays dual roles in Systemic lupus Erythematosus (SLE) where it may inhibit pro-inflammatory effector functions but seems to be also a main driver of the extrafollicular antibody response, outside of germinal centers (GC). In line, IL-10 promotes direct differentiation of activated B cells into plasma cells rather than stimulating a GC response. IL-10 is produced by B cells, myeloid cells, and certain T cell subsets, including extrafollicular T helper cells, which are phenotypically distinct from follicular helper T cells that are relevant for GC formation. In SLE patients and murine lupus models extrafollicular T helper cells have been reported to support ongoing extrafollicular formation of autoreactive plasma cells, despite the presence of GCs. Here, we discuss the role of IL-10 as driver of B cell responses, its impact on B cell proliferation, class switch, and plasma cells.

Recombinant HBsAg of the Wild-Type and the G145R Escape Mutant, included in the New Multivalent Vaccine against Hepatitis B Virus, Dramatically Differ in their Effects on Leukocytes from Healthy Donors In Vitro

Immune-escape hepatitis B virus (HBV) mutants play an important role in HBV spread. Recently, the multivalent vaccine Bubo^®-Unigep has been developed to protect against both wild-type HBV and the most significant G145R mutant. Here, we compared the effects of recombinant HBsAg antigens, wild-type and mutated at G145R, both included in the new vaccine, on activation of a human high-density culture of peripheral blood mononuclear cells (PBMC) in vitro. The antigens were used either alone or in combination with phytohemagglutinin (PHA). None of the antigens alone affected the expression of CD40, HLA-DR or CD279. Wild-type HBsAg enhanced CD86 and CD69 expression, and induced TNF-α, IL-10, and IFN-γ, regardless of the anti-HBsAg status of donor. In the presence of PHA, wild-type HBsAg had no effect on either of the tested surface markers, but increased IFN-γ and IL-10 and inhibited IL-2. In contrast, the G145R mutant alone did not affect CD86 expression, it induced less CD69, and stimulated IL-2 along with lowering levels of TNF-α, IL-10, and IFN-γ. The G145R mutant also suppressed PHA-induced activation of CD69. The dramatic differences in the immune responses elicited by wild-type HBsAg and the G145R mutant HBsAg suggest distinct adaptive capabilities of the G145R mutant HBV.

Antiparasitic potential of ethanolic extracts of Carpesii Fructus against Miamiensis avidus in hirame natural embryo cell line and their effects on immune response- and biotransformation-related genes

Scuticociliatosis, caused by Miamiensis avidus, is a severe parasitic disease affecting marine organisms, particularly Paralichthys olivaceus. The aim of this study was to assess the antiparasitic potential of ethanolic extracts of Carpesii Fructus (EECF), the dried fruit of Carpesium abrotanoides L., which is used in traditional Chinese medicine, in vitro. We found that 50%, 70%, and 100% EECF induced morphological changes in M. avidus, including reduced motility, cell shrinkage, and lysis. Nearly 100% cell lysis was observed in M. avidus after 2 h of treating with 100% EECF. After 24 h, the survival rates of M. avidus treated with 100%, 70%, and 50% EECF were 10%, 20%, and 30%, respectively. Additionally, the mRNA levels of immune response-related (IL-1β, IL-8, TNF-α, and CD8-α) and biotransformation-related (CYP1A, CYP1B, CYP3A4, and UGT2B19) genes increased with 70% and 100% EECF treatment and decreased with 50% EECF treatment following pretreatment with concanavalin A. The viability of hirame natural embryo (HINAE) cells was reduced by 50%, 70%, and 100% EECF (100 mg/L) and was between 67 and 80%. The IC₅₀ values of 50%, 70%, 90%, and 100% EECF in HINAE cells were 102.3, 42.93, 39.15, and 38.39 mg/L, respectively. These results indicated that 50% EECF was less toxic to HINAE cells than 70% or 100% EECF, while still exhibiting antiparasitic activity against M. avidus. Therefore, we demonstrated the role of EECF as a natural antiparasitic agent against M. avidus. Our findings suggest that Carpesii Fructus has potential use as an antiparasitic agent in the aquaculture industry.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

Immunological memory in rheumatic inflammation - a roadblock to tolerance induction

Why do we still have no cure for chronic inflammatory diseases? One reason could be that current therapies are based on the assumption that chronic inflammation is driven by persistent 'acute' immune reactions. Here we discuss a paradigm shift by suggesting that beyond these reactions, chronic inflammation is driven by imprinted, pathogenic 'memory' cells of the immune system. This rationale is based on the observation that in patients with chronic inflammatory rheumatic diseases refractory to conventional immunosuppressive therapies, therapy-free remission can be achieved by resetting the immune system; that is, by ablating immune cells and regenerating the immune system from stem cells. The success of this approach identifies antigen-experienced and imprinted immune cells as essential and sufficient drivers of inflammation. The 'dark side' of immunological memory primarily involves memory plasma cells secreting pathogenic antibodies and memory T lymphocytes secreting pathogenic cytokines and chemokines, but can also involve cells of innate immunity. New therapeutic strategies should address the persistence of these memory cells. Selective targeting of pathogenic immune memory cells could be based on their specificity, which is challenging, or on their lifestyle, which differs from that of protective immune memory cells, in particular for pathogenic T lymphocytes. The adaptations of such pathogenic memory cells to chronic inflammation offers entirely new therapeutic options for their selective ablation and the regeneration of immunological tolerance.

Bioassay-guided isolation of anti-inflammatory constituents from Celtis sinensis leaves

Ginkgo acids (GAs) in ginkgo products usually lead to allergies or liver toxicity. In this study, the GA-induced toxicity was attenuated and Con A-induced T-lymphocyte proliferation was inhibited by extracts of Celtis sinensis leaves (ECSL). So, the active ingredients in ECSL were studied to solve the problems caused by GAs. First, the eight components of MeOH extracts were determined by HPLC-DAD/LC-MS. Then, the 12 active ingredients were separated based on the anti-inflammatory activity. Lymphocyte conversion showed that the inhibition rates of apigenin, quercetin, and isovitexin at 100 μM on Con A-activated proliferation of T cells were up to 82.46%, 62.86% and 42.76%, respectively. The inhibition rate on the LPS-induced NO release in RAW 264.7 cells of quercetin, apigenin, isovitexin, and vitexin were exceeding 80% at 100 μM. Taken together, the material foundation for the screen of GAs toxicity-attenuated ingredients were provided here. PRACTICAL APPLICATIONS: Ginkgo biloba extracts (EGBs) have been conducted to develop functional food which could increase blood circulation and enhance memory. Nevertheless, people in consumption of ginkgo products, often caused severe allergic reactions due to the potential allergens identified ginkgolic acids (GAs) of ginkgo products. We first find that the extracts of Celtis sinensis leaves can reduce GAs-induced damage on HepG2 liver cells. Then, the bioactive compounds in C. sinensis leaves were separated and purified based on anti-inflammatory activities against T cells. Quercetin, apigenin, and isovitexin showed well anti-inflammatory activities against Con A-activated T-lymphocytes and LPS activated RAW 264.7 macrophages. However, quercetin and apigenin are flavones O-glycosides which are rich in Ginkgo biloba. To solve the problems in Ginkgo biloba products caused by GAs, flavone C-glycoside (isovitexin) may be used for the further study in GAs toxicity-reduction.

Suppression of Staphylococcus aureus Superantigen-Independent Interferon Gamma Response by a Probiotic Polysaccharide

Staphylococcus aureus is a Gram-positive opportunistic pathogen that causes a variety of diseases. Bloodstream infection is the most severe, with mortality rates reaching 20 to 50%. Exopolysaccharide (EPS) from the probiotic Bacillus subtilis reduces bacterial burden and inflammation during S. aureus bloodstream infection in mice. Protection is due, in part, to hybrid macrophages that restrict S. aureus growth through reactive oxygen species and to limiting superantigen-induced T cell activation and interferon gamma (IFN-γ) production during infection. A decrease in IFN-γ production was observed within 24 h after infection, and here, we investigated how EPS abrogates its production. We discovered that S. aureus uses a rapid, superantigen-independent mechanism to induce host IFN-γ and that this is mediated by interleukin-12 (IL-12) activation of NK cells. Furthermore, we found that EPS limits IFN-γ production by modulating host immunity in a Toll-like receptor 4 (TLR4)-dependent manner, a signaling pathway that is required for EPS-mediated protection from S. aureus infection in vivo We conclude that EPS protects hosts from acute bloodstream S. aureus infection not only by inducing macrophages that restrict S. aureus growth and inhibit superantigen-activated T cells but also by limiting NK cell production of IFN-γ after S. aureus infection in a TLR4-dependent manner.

Inhibition of fracture healing in the presence of contamination by Staphylococcus aureus: Effects of growth state and immune response

Extremity injuries comprise a significant portion of trauma, affecting quality of life, financial burden, and return to duty. Bacterial contamination is commonly associated with failure to heal, despite antibiotic treatment, suggesting that additional therapies must be developed to combat these complications. Treatment failure is likely due to the presence of resistant microbial communities known as biofilms. Biofilm bacteria are able to elicit a direct inhibition of healing through a multitude of known factors. However, they likely also inhibit healing through alteration of the inflammatory response. As inflammation is a critical step in fracture healing, how the presence of biofilm bacteria shifts this response to one that is suboptimal for healing is an important consideration that is currently understudied. The profile of inflammatory factors in response to biofilm bacteria is unique and distinct from those induced during normal healing or by planktonic bacteria alone. This review will examine the presence of inflammatory factors during normal healing and those induced by contaminating bacteria, and will discuss how these differences may ultimately lead to nonunion. Specifically, this review will focus on the Th1/Th2/Th17 type inflammatory responses and how shifts in the balance of these responses during infection can lead to both ineffective clearance and disruption of fracture healing. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1845-1854, 2017.

Adequate immune response ensured by binary IL-2 and graded CD25 expression in a murine transfer model

The IL-2/IL-2Ralpha (CD25) axis is of central importance for the interplay of effector and regulatory T cells. Nevertheless, the question how different antigen loads are translated into appropriate IL-2 production to ensure adequate responses against pathogens remains largely unexplored. Here we find that at single cell level, IL-2 is binary (digital) and CD25 is graded expressed whereas at population level both parameters show graded expression correlating with the antigen amount. Combining in vivo data with a mathematical model we demonstrate that only this binary IL-2 expression ensures a wide linear antigen response range for Teff and Treg cells under real spatiotemporal conditions. Furthermore, at low antigen concentrations binary IL-2 expression safeguards by its spatial distribution selective STAT5 activation only of closely adjacent Treg cells regardless of their antigen specificity. These data show that the mode of IL-2 secretion is critical to tailor the adaptive immune response to the antigen amount.

DOI:http://dx.doi.org/10.7554/eLife.20616.001

A Simple Microfluidic Platform for Long-Term Analysis and Continuous Dual-Imaging Detection of T-Cell Secreted IFN-γ and IL-2 on Antibody-Based Biochip

The identification and characterization, at the cellular level, of cytokine productions present a high interest for both fundamental research and clinical studies. However, the majority of techniques currently available (ELISA, ELISpot, flow cytometry, etc.) have several shortcomings including, notably, the assessment of several cytokines in relation to individual secreting cells and the monitoring of living cell responses for a long incubation time. In the present work, we describe a system composed of a microfluidic platform coupled with an antibody microarray chip for continuous SPR imaging and immunofluorescence analysis of cytokines (IL-2 and IFN-γ) secreted by T-Lymphocytes, specifically, and stably captured on the biochip under flow upon continued long-term on-chip culture (more than 24 h).

Natural indoles, indole-3-carbinol (I3C) and 3,3'-diindolylmethane (DIM), attenuate staphylococcal enterotoxin B-mediated liver injury by downregulating miR-31 expression and promoting caspase-2-mediated apoptosis

Staphylococcal enterotoxin B (SEB) is a potent superantigen capable of inducing inflammation characterized by robust immune cell activation and proinflammatory cytokine release. Exposure to SEB can result in food poisoning as well as fatal conditions such as toxic shock syndrome. In the current study, we investigated the effect of natural indoles including indole-3-carbinol (I3C) and 3,3’-diindolylmethane (DIM) on SEB-mediated liver injury. Injection of SEB into D-galactosamine-sensitized female C57BL/6 mice resulted in liver injury as indicated by an increase in enzyme aspartate transaminase (AST) levels, induction of inflammatory cytokines, and massive infiltration of immune cells into the liver. Administration of I3C and DIM (40mg/kg), by intraperitonal injection, attenuated SEB-induced acute liver injury, as evidenced by decrease in AST levels, inflammatory cytokines and cellular infiltration in the liver. I3C and DIM triggered apoptosis in SEB-activated T cells primarily through activation of the intrinsic mitochondrial pathway. In addition, inhibitor studies involving caspases revealed that I3C and DIM-mediated apoptosis in these activated cells was dependent on caspase-2 but independent of caspase-8, 9 and 3. In addition, I3C and DIM caused a decrease in Bcl-2 expression. Both compounds also down-regulated miR-31, which directly targets caspase-2 and influences apoptosis in SEB-activated cells. Our data demonstrate for the first time that indoles can effectively suppress acute hepatic inflammation caused by SEB and that this may be mediated by decreased expression of miR-31 and consequent caspase-2-dependent apoptosis in T cells.

Individual T helper cells have a quantitative cytokine memory

The probabilistic expression of cytokine genes in differentiated T helper (Th) cell populations remains ill defined. By single-cell analyses and mathematical modeling, we show that one stimulation featured stable cytokine nonproducers as well as stable producers with wide cell-to-cell variability in the magnitude of expression. Focusing on interferon-γ (IFN-γ) expression by Th1 cells, mathematical modeling predicted that this behavior reflected different cell-intrinsic capacities and not mere gene-expression noise. In vivo, Th1 cells sort purified by secreted IFN-γ amounts preserved a quantitative memory for both probability and magnitude of IFN-γ re-expression for at least 1 month. Mechanistically, this memory resulted from quantitatively distinct transcription of individual alleles and was controlled by stable expression differences of the Th1 cell lineage-specifying transcription factor T-bet. Functionally, Th1 cells with graded IFN-γ production competence differentially activated Salmonella-infected macrophages for bacterial killing. Thus, individual Th cells commit to produce distinct amounts of a given cytokine, thereby generating functional intrapopulation heterogeneity.

Modelling the interaction between the host immune response, bacterial dynamics and inflammatory damage in comparison with immunomodulation and vaccination experiments

The immune system is a complex system of chemical and cellular interactions that responds quickly to queues that signal infection and then reverts to a basal level once the challenge is eliminated. Here, we present a general, four-component model of the immune system's response to a Staphylococcal aureus (S. aureus) infection, using ordinary differential equations. To incorporate both the infection and the immune system, we adopt the style of compartmenting the system to include bacterial dynamics, damage and inflammation to the host, and the host response. We incorporate interactions not previously represented including cross-talk between inflammation/damage and the infection and the suppression of the anti-inflammatory pathway in response to inflammation/damage. As a result, the most relevant equilibrium of the system, representing the health state, is an all-positive basal level. The model is able to capture eight different experimental outcomes for mice challenged with intratibial osteomyelitis due to S. aureus, primarily involving immunomodulation and vaccine therapies. For further validation and parameter exploration, we perform a parameter sensitivity analysis which suggests that the model is very stable with respect to variations in parameters, indicates potential immunomodulation strategies and provides a possible explanation for the difference in immune potential for different mouse strains.

Staphylococcal enterotoxin B-induced microRNA-155 targets SOCS1 to promote acute inflammatory lung injury

Staphylococcal enterotoxin B (SEB) causes food poisoning in humans. It is considered a biological weapon, and inhalation can trigger lung injury and sometimes respiratory failure. Being a superantigen, SEB initiates an exaggerated inflammatory response. While the role of microRNAs (miRNAs) in immune cell activation is getting increasing recognition, their role in the regulation of inflammatory disease induced by SEB has not been studied. In this investigation, we demonstrate that exposure to SEB by inhalation results in acute inflammatory lung injury accompanied by an altered miRNA expression profile in lung-infiltrating cells. Among the miRNAs that were significantly elevated, miR-155 was the most overexpressed. Interestingly, miR-155(-/-) mice were protected from SEB-mediated inflammation and lung injury. Further studies revealed a functional link between SEB-induced miR-155 and proinflammatory cytokine gamma interferon (IFN-γ). Through the use of bioinformatics tools, suppressor of cytokine signaling 1 (SOCS1), a negative regulator of IFN-γ, was identified as a potential target of miR-155. While miR-155(-/-) mice displayed increased expression of Socs1, the overexpression of miR-155 led to its suppression, thereby enhancing IFN-γ levels. Additionally, the inhibition of miR-155 resulted in restored Socs1expression. Together, our data demonstrate an important role for miR-155 in promoting SEB-mediated inflammation in the lungs through Socs1 suppression and suggest that miR-155 may be an important target in preventing SEB-mediated inflammation and tissue injury.

Impact of T cell selection methods in the success of clinical adoptive immunotherapy

Chemotherapy and/or radiotherapy regular regimens used for conditioning of recipients of hematopoietic stem cell transplantation (SCT) induce a period of transient profound immunosuppression. The onset of a competent immunological response, such as the appearance of viral-specific T cells, is associated with a lower incidence of viral infections after haematopoietic transplantation. The rapid development of immunodominant peptide virus screening together with advances in the design of genetic and non-genetic viral- and tumoural-specific cellular selection strategies have opened new strategies for cellular immunotherapy in oncologic recipients who are highly sensitive to viral infections. However, the rapid development of cellular immunotherapy in SCT has disclosed the role of the T cell selection method in the modulation of functional cell activity and of in vivo secondary effects triggered following immunotherapy.

Natural indoles, indole-3-carbinol and 3,3'-diindolymethane, inhibit T cell activation by staphylococcal enterotoxin B through epigenetic regulation involving HDAC expression

Staphylococcal enterotoxin B (SEB) is a potent exotoxin produced by the Staphylococcus aureus. This toxin is classified as a superantigen because of its ability to directly bind with MHC-II class molecules followed by activation of a large proportion of T cells bearing specific Vβ-T cell receptors. Commonly associated with classic food poisoning, SEB has also been shown to induce toxic shock syndrome, and is also considered to be a potential biological warfare agent because it is easily aerosolized. In the present study, we assessed the ability of indole-3-carbinol (I3C) and one of its byproducts, 3,3'-diindolylmethane (DIM), found in cruciferous vegetables, to counteract the effects of SEB-induced activation of T cells in mice. Both I3C and DIM were found to decrease the activation, proliferation, and cytokine production by SEB-activated Vβ8(+) T cells in vitro and in vivo. Interestingly, inhibitors of histone deacetylase class I (HDAC-I), but not class II (HDAC-II), showed significant decrease in SEB-induced T cell activation and cytokine production, thereby suggesting that epigenetic modulation plays a critical role in the regulation of SEB-induced inflammation. In addition, I3C and DIM caused a decrease in HDAC-I but not HDAC-II in SEB-activated T cells, thereby suggesting that I3C and DIM may inhibit SEB-mediated T cell activation by acting as HDAC-I inhibitors. These studies not only suggest for the first time that plant-derived indoles are potent suppressors of SEB-induced T cell activation and cytokine storm but also that they may mediate these effects by acting as HDAC inhibitors.

Suppression of the inflammatory immune response prevents the development of chronic biofilm infection due to methicillin-resistant Staphylococcus aureus

Staphylococcus aureus is a common cause of prosthetic implant infections, which can become chronic due to the ability of S. aureus to grow as a biofilm. Little is known about adaptive immune responses to these infections in vivo. We hypothesized that S. aureus elicits inflammatory Th1/Th17 responses, associated with biofilm formation, instead of protective Th2/Treg responses. We used an adapted mouse model of biofilm-mediated prosthetic implant infection to determine chronic infection rates, Treg cell frequencies, and local cytokine levels in Th1-biased C57BL/6 and Th2-biased BALB/c mice. All C57BL/6 mice developed chronic S. aureus implant infection at all time points tested. However, over 75% of BALB/c mice spontaneously cleared the infection without adjunctive therapy and demonstrated higher levels of Th2 cytokines and anti-inflammatory Treg cells. When chronic infection rates in mice deficient in the Th2 cytokine interleukin-4 (IL-4) via STAT6 mutation in a BALB/c background were assessed, the mice were unable to clear the S. aureus implant infection. Additionally, BALB/c mice depleted of Treg cells via an anti-CD25 monoclonal antibody (MAb) were also unable to clear the infection. In contrast, the C57BL/6 mice that were susceptible to infection were able to eliminate S. aureus biofilm populations on infected intramedullary pins once the Th1 and Th17 responses were diminished by MAb treatment with anti-IL-12 p40. Together, these results indicate that Th2/Treg responses are mechanisms of protection against chronic S. aureus implant infection, as opposed to Th1/Th17 responses, which may play a role in the development of chronic infection.

Murine immune response to a chronic Staphylococcus aureus biofilm infection

Staphylococcus aureus has reemerged as an important human pathogen in recent decades. Although many infections caused by this microbial species persist through a biofilm mode of growth, little is known about how the host's adaptive immune system responds to these biofilm infections. In this study, S. aureus cells adhered to pins in culture and were subsequently inserted into the tibiae of C57BL/6 mice, with an infecting dose of 2 × 10⁵ CFU. This model was utilized to determine local cytokine levels, antibody (Ab) function, and T cell populations at multiple time points throughout infection. Like human hosts, S. aureus implant infection was chronic and remained localized in 100% of C57BL/6 mice at a consistent level of approximately 10(7) CFU/gram bone tissue after day 7. This infection persisted locally for >49 days and was recalcitrant to clearance by the host immune response and antimicrobial therapy. Local inflammatory cytokines of the Th1 (interleukin-2 [IL-2], IL-12 p70, tumor necrosis factor alpha [TNF-α], and IL-1β) and Th17 (IL-6 and IL-17) responses were upregulated throughout the infection, except IL-12 p70, which dwindled late in the infection. In addition, Th1 Ab subtypes against a biofilm antigen (SA0486) were upregulated early in the infection, while Th2 Abs and anti-inflammatory regulatory T cells (Tregs) were not upregulated until later. These results indicate that early Th1 and Th17 inflammatory responses and downregulated Th2 and Treg responses occur during the development of a chronic biofilm implant infection. This unrestrained inflammatory response may cause tissue damage, thereby enabling S. aureus to attach and thrive in a biofilm mode of growth.

Cytokine reporter mice in immunological research: perspectives and lessons learned

Cytokines are soluble messenger molecules with important regulatory functions throughout the immune system. 'Cytokine reporter' strains express marker molecules under control of elements from cytokine genes allowing for easy identification of their cellular sources. Such systems are well-accepted tools for research of cytokine function. The value of these strains lies in the ability to perform experiments relying on identification and isolation of live cytokine-expressing cells, provided that the reporter faithfully reflects the proper cytokine mRNA and protein production. As more diverse cell subsets are defined by their cytokine expression, the field has adapted with the generation of more sophisticated strains. In this review we summarize the evolution of cytokine detection methods and give examples of knowledge gained using cytokine reporter mice for cell types expressing interferon-γ and interleukin-4, -10 and -17. We also discuss current options for generating such reporter strains and their potential pitfalls.

Staphylococcal enterotoxins

Staphylococcus aureus (S. aureus) is a Gram positive bacterium that is carried by about one third of the general population and is responsible for common and serious diseases. These diseases include food poisoning and toxic shock syndrome, which are caused by exotoxins produced by S. aureus. Of the more than 20 Staphylococcal enterotoxins, SEA and SEB are the best characterized and are also regarded as superantigens because of their ability to bind to class II MHC molecules on antigen presenting cells and stimulate large populations of T cells that share variable regions on the β chain of the T cell receptor. The result of this massive T cell activation is a cytokine bolus leading to an acute toxic shock. These proteins are highly resistant to denaturation, which allows them to remain intact in contaminated food and trigger disease outbreaks. A recognized problem is the emergence of multi-drug resistant strains of S. aureus and these are a concern in the clinical setting as they are a common cause of antibiotic-associated diarrhea in hospitalized patients. In this review, we provide an overview of the current understanding of these proteins.

Vaccine development in Staphylococcus aureus: taking the biofilm phenotype into consideration

Vaccine development against pathogenic bacteria is an imperative initiative as bacteria are gaining resistance to current antimicrobial therapies and few novel antibiotics are being developed. Candidate antigens for vaccine development can be identified by a multitude of high-throughput technologies that were accelerated by access to complete genomes. While considerable success has been achieved in vaccine development against bacterial pathogens, many species with multiple virulence factors and modes of infection have provided reasonable challenges in identifying protective antigens. In particular, vaccine candidates should be evaluated in the context of the complex disease properties, whether planktonic (e.g. sepsis and pneumonia) and/or biofilm associated (e.g. indwelling medical device infections). Because of the phenotypic differences between these modes of growth, those vaccine candidates chosen only for their efficacy in one disease state may fail against other infections. This review will summarize the history and types of bacterial vaccines and adjuvants as well as present an overview of modern antigen discovery and complications brought about by polymicrobial infections. Finally, we will also use one of the better studied microbial species that uses differential, multifactorial protein profiles to mediate an array of diseases, Staphylococcus aureus, to outline some of the more recently identified problematic issues in vaccine development in this biofilm-forming species.

Dietary plasma protein supplements prevent the release of mucosal proinflammatory mediators in intestinal inflammation in rats

Spray-dried plasma (SDP) is a complex mixture of active proteins that modulates the immune response of gut-associated lymphoid tissue. We examined whether SDP and Ig concentrate (IC) supplementation could modulate cytokine expression and inflammatory mediators in rats challenged with Staphylococcus aureus enterotoxin B (SEB). Wistar-Lewis rats were fed diets supplemented with SDP (8% wt:wt), IC (1.5% wt:wt), or milk proteins (control diet) from weaning (d 21) to d 34 after birth. On d 32 and 35, the rats were given SEB (0.5 mg/kg; intraperitoneal). Six hours after the second SEB dose, jejunal mucosa and Peyer's patches (PP) from the small intestine were collected. The cytokines interferon-gamma (IFNgamma), tumor necrosis factor-alpha (TNFalpha), interleukin (IL)-6, IL-10, transforming growth factor-beta (TGFbeta), and leukotrienne B(4) (LTB(4)) were analyzed using commercial kits. SEB increased the release of proinflammatory mediators (IFNgamma, TNFalpha, IL-6, and LTB(4)) in PP (P < 0.05) and in the mucosa (P < 0.05). In both tissues, SDP prevented the increase in IFNgamma, IL-6, and LTB(4) induced by SEB (P < 0.05). IC reduced the expression of TNFalpha and LTB(4) in PP and mucosa (P < 0.05). SDP supplementation increased IL-10 and mature TGFbeta concentrations in intestinal mucosa from both inflamed and noninflamed rats. Both SDP and IC increased the mature:total TGFbeta ratio (all P < 0.05). Both supplements were effective at preventing the SEB-induced increase in proinflammatory:antiinflammatory cytokine ratios in PP and mucosa and in serum. The preventive effects of plasma supplements on intestinal inflammation involve modulation of intestinal cytokines, characterized by an increased expression of antiinflammatory cytokines.

Nonoverlapping expression of IL10, IL12p40, and IFNgamma mRNA in the marginal zone and T cell zone of the spleen after antigenic stimulation

The differentiation of CD4(+) T cells is regulated by cytokines locally within the compartments of secondary lymphoid organs during adaptive immune responses. Quantitative data about the expression of cytokine mRNAs within the T and B cell zones of lymphoid organs are lacking. In this study, we assessed the expression of multiple cytokine genes within the lymphoid compartments of the spleen of rats after two types of stimulation. First, the spleen was stimulated directly by a blood-derived Ag. Second, the spleen was stimulated indirectly by incoming lymphocytes that had been activated and released during a proceeding immune response at a distant tissue site. Using laser microdissection, we show that the expression of cytokine mRNAs was compartment specific, transient, and preceded cell proliferation after the direct antigenic stimulation. Surprisingly, the indirect stimulation by incoming activated lymphocytes induced similar cytokines in the T cell zone. However, the nonoverlapping expression was lost and IL10 appeared as the major cytokine in all compartments. Thus, tracking two types of immune activation without disturbing the integrity of structures reveals distinct and overlapping events in the compartments of the spleen. This information adds a new dimension to the understanding of immune responses in vivo.

Apoptotic cells protect mice against lipopolysaccharide-induced shock

LPS is a main causative agent of septic shock. There is a lack of effective therapies. In vitro studies have shown that uptake of apoptotic cells actively inhibits the secretion by activated macrophages (Mphi) of proinflammatory mediators such as TNF-alpha and that such uptake increases the antiinflammatory and immunosuppressive cytokine TGF-beta. We therefore investigated the protective effect of apoptotic cells against LPS-induced endotoxic shock in mice. The current report is the first study to demonstrate that administration of apoptotic cells can protect mice from LPS-induced death, even when apoptotic cells were administered 24 h after LPS challenge. The beneficial effects of administration of apoptotic cells included 1) reduced circulating proinflammatory cytokines, 2) suppression of polymorphonuclear neutrophil infiltration in target organs, and 3) decreased serum LPS levels. LPS can quickly bind to apoptotic cells and these LPS-coated apoptotic cells can be recognized and cleared by Mphi in a CD14/thrombospondin/vitronectin receptor-dependent manner, accompanied with suppression of TNF-alpha and enhancement of IL-10 expression by LPS-activated Mphi. Apoptotic cells may therefore have therapeutic potential for the treatment of septic shock.

Relationship of varying patterns of cytokine production to the anorexic and neuroendocrine effects of repeated Staphylococcal enterotoxin A exposure

Staphylococcal enterotoxin A (SEA) is a superantigen that stimulates T cells and induces the production of multiple cytokines. Previous studies have shown that SEA augments gustatory neophobia and activates the hypothalamic-pituitary-adrenal (HPA) axis. This study aimed to determine if the cytokine response, behavioral effects, and HPA axis activation persisted after repeated SEA treatment. Male C57BL/6J mice were given 1-4 intraperitoneal injections of 5 microg SEA, after which food intake, corticosterone, or peripheral cytokines were measured. In a series of experiments, it was found that secondary exposure to SEA two or three days after priming increased corticosterone, but attenuated splenic TNFalpha, while augmenting IL-1beta, IL-2, and IFNgamma. The anorexic response was intact after secondary exposure, but absent after a third injection, which was still able to elevate corticosterone. It is unlikely that IL-1 mediated the persistent effects on corticosterone, since this was increased in groups lacking corticosterone elevations. Similarly, TNFalpha was only modestly elevated under repeated SEA conditions that elevated plasma corticosterone. This attenuation appeared to be inversely related to the levels of IL-10, the production of which incrementally rose with each successive injection. In conclusion, repeated exposure to SEA activates the HPA axis and alters behavior. However, there may be dissociation between the behavioral and endocrine effects of SEA with increased SEA exposure. Furthermore, it is possible that while TNFalpha was previously shown to be important in response to acute SEA-induced HPA axis activation, further exposure to SEA elicits other cytokines that may exert neuromodulatory effects through sensitization and/or synergistic mechanisms.

Digital NFATc2 activation per cell transforms graded T cell receptor activation into an all-or-none IL-2 expression

The expression of interleukin-2 (IL-2) is a key event in T helper (Th) lymphocyte activation, controlling both, the expansion and differentiation of effector Th cells as well as the activation of regulatory T cells. We demonstrate that the strength of TCR stimulation is translated into the frequency of memory Th cells expressing IL-2 but not into the amount of IL-2 per cell. This molecular switch decision for IL-2 expression per cell is located downstream of the cytosolic Ca²⁺ level. Here we show that in a single activated Th cell, NFATc2 activation is digital but NF-κB activation is graded after graded T cell receptor (TCR) signaling. Subsequently, NFATc2 translocates into the nucleus in an all-or-none fashion per cell, transforming the strength of TCR-stimulation into the number of nuclei positive for NFATc2 and IL-2 transcription. Thus, the described NFATc2 switch regulates the number of Th cells actively participating in an immune response.

The pro- and anti-inflammatory potential of IL-12: the dual role of Th1 cells

The differentiation of T-helper (Th) lymphocytes into various types of T-helper effector and memory cells with distinct functions depending on the type of concomitant signals they receive upon activation is a critical event determining the course of an immune reaction. Th1 cells characterized by the expression of IFN-gamma and the recently described Th17 cells promote inflammation and are critically involved in the induction and maintenance of autoimmunity, whereas the secretion of IL-4 is a hallmark of Th2 cells mediating protection from parasites and allergy. Original stimulation in the presence of IL-12 results in the imprinting of Th1 memory cells for the expression of IFN-gamma by expression of the transcription factor T-bet and epigenetic modification of the ifngamma gene. It has been demonstrated that Th1 cells are potent inducers of inflammation. However, in the chronic phase of such inflammation, the regulatory potential of IL-12 and Th1 cells themselves may play an important role in limiting immunopathology.

Upregulation of CD4+ NKT Cells Is Important for Allograft Survival in Staphylococcal-Enterotoxin-B-Treated Rats after High-Risk Corneal Transplantation

OBJECTIVE

To study the role of CD4+ natural killer T (NKT) cells in staphylococcal-enterotoxin-B (SEB)-treated rats after high-risk corneal transplantation.

METHOD

Fisher 344 donor corneas were transplanted into Lewis recipients. Corneal neovascularization was induced by sutures. All the recipients were randomly divided into 3 groups. The SEB group was intraperitoneally injected with SEB at a concentration of 75 microg/kg. The drug combination group received SEB and dexamethasone at a concentration of 5 mg/ml. The control group received saline buffer. All transplants were evaluated for 30 days. Ten days after transplantation, 3 recipients in each group were sacrificed for immunological study.

RESULT

The survival time of the allografts in the SEB group was 12.50 +/- 1.41 days, much longer than in the control group (7.30 +/- 0.67 days) and the drug combination group (10.38 +/- 3.07 days). The lymphocyte proliferation ability was the weakest and the percentage of CD4+ NKT cells in both the spleen and the mandibular lymph nodes was the highest in the SEB group, while the percentage of CD4+ and CD8+ cells was the lowest in the drug combination group. IL-2 in the aqueous humor and the serum was lower while IL-10 was higher in the SEB group than in the other 2 groups.

CONCLUSION

SEB prolongs allograft survival in rat high-risk corneal transplantation. This effect seems to be mediated by the upregulation of CD4+ NKT cells.

Expression of IL-10 in Th memory lymphocytes is conditional on IL-12 or IL-4, unless the IL-10 gene is imprinted by GATA-3

In Th1 and Th2 memory lymphocytes, the genes for the cytokines interleukin (IL)-4 and interferon-gamma (IFN-gamma) are imprinted for expression upon restimulation. This cytokine memory is based on expression of the transcription factors T-bet for IFN-gamma, and GATA-3 for IL-4, and epigenetic modification of the cytokine genes. In Th2 cells, expression of the cytokine IL-10 is also induced by GATA-3. Here, we show that this induction is initially not accompanied by epigenetic modification of the IL-10 gene. Only after repeated restimulation of a memory Th2 cell in the presence of IL-4, extensive histone acetylation of the IL-10 gene is detectable. This epigenetic imprinting correlates with the development of a memory for IL-10 in repeatedly restimulated Th2 cells. In Th1 cells, IL-10 expression is induced by IL-12, but the IL-10 gene lacks detectable histone acetylation. Accordingly, IL-10 expression in restimulated memory Th1 cells remains conditional on the presence of IL-12. This finding defines a potential anti-inflammatory role for IL-12 in Th1 recall responses. While in primary Th1 responses IL-12 is required to induce expression of the pro-inflammatory cytokine IFN-gamma, in secondary Th1 responses IFN-gamma re-expression is independent of IL-12, which still is able to induce expression of the anti-inflammatory cytokine IL-10.

CD4(+)CD25(-)Foxp3(-) Th1 cells are the source of IL-10-mediated immune suppression in chronic cutaneous leishmaniasis

Nonhealing forms of leishmaniasis in humans are commonly associated with elevated levels of the deactivating cytokine IL-10, and in the mouse, normally chronic infections can be cleared in the absence of IL-10. Using a Leishmania major strain that produces nonhealing dermal lesions in a T helper type 1 (Th1) cell–polarized setting, we have analyzed the cellular sources of IL-10 and their relative contribution to immune suppression. IL-10 was produced by innate cells, as well as CD4⁺CD25⁺Foxp3⁺ and CD4⁺CD25⁻Foxp3⁻ T cells in the chronic lesion. Nonetheless, only IL-10 production by antigen-specific CD4⁺CD25⁻Foxp3⁻ T cells, the majority of which also produced IFN-γ, was necessary for suppression of acquired immunity in Rag^−/− reconstituted mice. Surprisingly, Rag^−/− mice reconstituted with naive CD4⁺ T cells depleted of natural T regulatory cells developed more severe infections, associated with elevated levels of IL-10 and, especially, Th2 cytokines in the site. The data demonstrate that IL-10–producing Th1 cells, activated early in a strong inflammatory setting as a mechanism of feedback control, are the principal mediators of T cell–derived IL-10–dependent immune suppression in a chronic intracellular infection.

Phenotypic analysis of B-cells and plasma cells

B-cells and antibody-secreting plasma cells are key players in protective immunity, but also in autoimmune disease. To understand their various functions in the initiation and maintenance of autoimmune pathology, a detailed dissection of their functional diversity is mandatory. This requires a detailed phenotypic classification of the diversity of B-cells. Here, technologies of immunocytometry and ELISpot are described in detail, and their value for phenotypic characterization of cells of the B lineage, as well as for preparative cell sorting, to further characterize them functionally and on the molecular level are described.

Is PR3-ANCA formation initiated in Wegener's granulomatosis lesions? Granulomas as potential lymphoid tissue maintaining autoantibody production

In Wegener's granulomatosis (WG), antiproteinase 3 (PR3) autoantibodies (PR3-ANCA) are crucial in the development of generalized vasculitis. Wegener's pathognomonic lesion, a granulomatous inflammation of the upper and lower respiratory tract, contains abundant lymphocytes and macrophages. Lymphocyte clusters in germinal center-like formation within the granulomatous lesion are frequently observed, which suggests antigen-driven B cell maturation. Wegener's autoantigen PR3, the target for autoreactive B and T cells, is expressed in granulomatous lesions. Disease progression in WG is accompanied by a profound generalized alteration of T cell differentiation with an increase of effector memory T cells (CD4(+)CD28(-)). The cytokine profile suggests an aberrant Th1-type response either to an environmental trigger and/or the autoantigen PR3 itself. Staphylococcus aureus, a risk factor for disease exacerbation, is widely present in the upper airways in WG. The Ig gene repertoire from WG lesions indicates a predominance of VH3+ B cells with affinity to PR3 as well as to the S. aureus B cell superantigen SPA. Hence, within the WG lesion, S. aureus might support the maturation of PR3-affinity B cells that enter a germinal center reaction in contact with PR3 and T cells and expand, leading to PR3-ANCA production. Thus, granulomatous lesions could represent a potential lymphoid tissue-maintaining autoantibody production rather than a simple, random leukocyte accumulation in WG.

Identification of Staphylococcus aureus proteins recognized by the antibody-mediated immune response to a biofilm infection

Staphylococcus aureus causes persistent, recurrent infections (e.g., osteomyelitis) by forming biofilms. To survey the antibody-mediated immune response and identify those proteins that are immunogenic in an S. aureus biofilm infection, the tibias of rabbits were infected with methicillin-resistant S. aureus to produce chronic osteomyelitis. Sera were collected prior to infection and at 14, 28, and 42 days postinfection. The sera were used to perform Western blot assays on total protein from biofilm grown in vitro and separated by two-dimensional gel electrophoresis. Those proteins recognized by host antibodies in the harvested sera were identified via matrix-assisted laser desorption ionization-time of flight analysis. Using protein from mechanically disrupted total and fractionated biofilm protein samples, we identified 26 and 22 immunogens, respectively. These included a cell surface-associated beta-lactamase, lipoprotein, lipase, autolysin, and an ABC transporter lipoprotein. Studies were also performed using microarray analyses and confirmed the biofilm-specific up-regulation of most of these genes. Therefore, although the biofilm antigens are recognized by the immune system, the biofilm infection can persist. However, these proteins, when delivered as vaccines, may be important in directing the immune system toward an early and effective antibody-mediated response to prevent chronic S. aureus infections. Previous works have identified S. aureus proteins that are immunogenic during acute infections, such as sepsis. However, this is the first work to identify these immunogens during chronic S. aureus biofilm infections and to simultaneously show the global relationship between the antigens expressed during an in vivo infection and the corresponding in vitro transcriptomic and proteomic gene expression levels.

T cell zones of lymphoid organs constitutively express Th1 cytokine mRNA: specific changes during the early phase of an immune response

The cytokine milieu of the T cell zones in lymphoid organs is involved in the activation of naive T cells. Quantitative data regarding the local expression of cytokines are lacking. Therefore, the expression of Th1 (IL-2, IL-12p40, IFN-gamma), Th2 (IL-4, IL-10), as well as TGFbeta1 and IL-15 mRNA was studied after laser microdissection in the steady state and during an immune response in rats. Our results show that Th1 cytokines are preferentially found in lymphoid tissues and in the T cell zones, whereas Th2 cytokines are expressed throughout the organs and especially in the B cell zones. After injection of sheep RBC, IL-2 and IFN-gamma mRNA are significantly increased in the T cell zone only, a change not seen by analyzing the whole spleen. Studying the spatial and temporal expression of genes will reveal new insights into the regulation of immune responses.

LiveCount Assay: concomitant measurement of cytolytic activity and phenotypic characterisation of CD8(+) T-cells by flow cytometry

Tumour immunologists strive to develop efficient tumour vaccination and adoptive transfer therapies that enlarge the pool of tumour-specific and -reactive effector T-cells in vivo. To assess the efficiency of the various strategies, ex vivo assays are needed for the longitudinal monitoring of the patient's specific immune responses providing both quantitative and qualitative data. In particular, since tumour cell cytolysis is the end goal of tumour immunotherapy, routine immune monitoring protocols need to include a read-out for the cytolytic efficiency of Ag-specific cells. We propose to combine current immune monitoring techniques in a highly sensitive and reproducible multi-parametric flow cytometry based cytotoxicity assay that has been optimised to require low numbers of Ag-specific T-cells. The possibility of re-analysing those T-cells that have undergone lytic activity is illustrated by the concomitant detection of CD107a upregulation on the surface of degranulated T-cells. To date, the LiveCount Assay provides the only possibility of assessing the ex vivo cytolytic activity of low-frequency Ag-specific cytotoxic T-lymphocytes from patient material.

Systemic dissemination and persistence of Th2 and type 2 cells in response to infection with a strictly enteric nematode parasite

Oral infection with the nematode parasite Heligmosomoides polygyrus H. polygyrus is entirely restricted to the small intestine. Although the evoked Th2 response has been extensively studied in secondary lymphoid organs, little is known about the systemic dissemination of Th2 cells or type 2 associated eosinophils and basophils. In this study we use bicistronic 4get IL-4 reporter mice to directly visualize the type 2 response to H. polygyrus infection. We observed that CD4(+)/GFP(+) Th2 cells spread systemically and found that these cells accumulated in nonlymphoid "hot spots" in the liver, the lung airways, and the peritoneal cavity. Interestingly, the total number of Th2 cells in the peritoneal cavity was comparable to those found in the draining mesenteric lymph node or the spleen. Peritoneal Th2 cells were distinguished by an exceptionally low apoptotic potential and high expression of the intestinal homing receptor alpha(4)beta(7) integrin. CD4(+)/GFP(+) Th2 cells from these peripheral sites were fully functional as indicated by rapid IL-4 production upon polyclonal or Ag-specific restimulation. Th2 cells persisted in the intestinal tissue and the peritoneal cavity of drug-cured mice for weeks. The presence of peripheral memory Th2 cells in the intestine might be crucial for immunity to recall infections. These findings have important implications for the design of vaccination strategies because it may be necessary to establish and maintain memory CD4(+) T cells at the potential future site of infection.

Immunological monitoring of cancer vaccine therapy

Immunological treatment of malignant diseases in humans aiming at the induction and proliferation of antigen-specific T cells has made rapid progress in recent years. A growing number of tumour-associated antigens, potentially synergistic combinations with adjuvants, and various routes of application provide new opportunities for cancer vaccination. Therefore, a highly accurate assessment of vaccine-induced T cell responses is required. Three T cell assays (tetramers, intracellular cytokine flow cytometry and ELISPOT assay) have emerged as first-line methods for monitoring T cell induction during vaccination. These assays are relatively easy to perform, reliable, sensitive and allow an ex vivo T cell analysis at the single cell level. Although at this stage assays are not a defined surrogate marker for clinical efficacy, they already provide information concerning the immunological potency of a given vaccine. In particular, comparing immune responses under various treatment conditions will help to develop more clinically efficient tumour vaccination. Novel assays, such as CD107 staining, human leukocyte antigen/green fluorescent protein-antigen-presenting cells or microarrays, and assays determining functions, such as proliferation assays, are beginning to complement first-line monitoring assays.

Molecular mechanisms involved in the pathogenesis of septic shock

Pathogenesis of the development of sepsis is highly complex and has been the object of study for many years. The inflammatory phenomena underlying septic shock are described in this review, as well as the enzymes and genes involved in the cellular activation that precedes this condition. The most important molecular aspects are discussed, ranging from the cytokines involved and their respective transduction pathways to the cellular mechanisms related to accelerated catabolism and multi-organic failure.

The functional heterogeneity of type 1 effector T cells in response to infection is related to the potential for IFN-gamma production

The expression of IFN-gamma is a hallmark of Th1 cells and CD8(+) effector T cells and is the signature cytokine of type 1 responses. However, it is not known whether T cells are homogeneous in their capacity to produce IFN-gamma, whether this potential varies between tissues, and how it relates to the production of other effector molecules. In the present study we used bicistronic IFN-gamma-enhanced yellow fluorescent protein (IFN-gamma-eYFP) reporter mice (Yeti) and MHC class I tetramers to directly quantify IFN-gamma expression at the single cell level. The eYFP fluorescence of Th1 cells and CD8(+) effector T cells was broadly heterogeneous even before cell division and correlated with both the abundance of IFN-gamma transcripts and the secretion of IFN-gamma upon stimulation. CD4(+) and CD8(+) T cells of influenza-infected mice revealed a similarly heterogeneous IFN-gamma expression, and eYFP(high) cells were only found in the infected lung. Ag-specific T cells were in all examined tissues eYFP(+), but also heterogeneous in their reporter fluorescence, and eYFP(high) cells were also restricted to the infected lung. A similar heterogeneity was observed in Toxoplasma gondii-infected animals, but eYFP(high) cells were restricted to different tissues. Highly eYFP fluorescent cells produced elevated levels of proinflammatory cytokines and chemokines in addition to IFN-gamma, suggesting their coregulated expression as a functional unit in highly differentiated effector T cells.

Off balance: T-cells in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides

There is substantial evidence that T-cells are off balance in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides. Genetic risk factors may influence shaping of the TCR repertoire and regulatory control of T-cells in predisposed individuals. T-cells are found in inflammatory lesions. Vigorous Th1-type responses are seen in Wegener's granulomatosis and microscopic angiitis, whereas a Th2-type response predominates in Churg-Strauss syndrome. Oligoclonality and shortened telomers indicate antigen-driven clonal expansion and replicative senescence of T-cells in ANCA-associated vasculitides. Potent CD28(-) Th1-type cells displaying an effector-memory/late differentiated, senescent phenotype are expanded in peripheral blood and are found in granulomatous lesions in Wegener's granulomatosis. Differences in proliferative peripheral blood T-cell responses to the autoantigens proteinase 3 (PR3)- and myeloperoxidase (MPO) have not consistently been detected between patients with ANCA-associated vasculitides and healthy controls in vitro. To recognize an autoantigen, break tolerance, and maintain autoimmune disease T- and B-cells require particular triggers and lymphoid structures. There is preliminary evidence of lymphoid-like structures and possible maturation of autoreactive PR3-ANCA-specific B-cells in granulomatous lesions in Wegener's granulomatosis. Alteration of the T-cell response and anomalous autoantigen-presentation in lymphoid-structures could facilitate development of autoimmune disease in ANCA-associated vasculitides.

SEB combined with IL-1ra could prolong the survival of the rat allografts in high-risk corneal transplantation

PURPOSE

To determine whether the superantigen Staphylococcal enterotoxin B (SEB) combined with interleukin-1 receptor antagonist (IL-1ra) prolong allograft survival better than individual agents in high-risk corneal transplantation in a rat model.

METHODS

Fisher 344 donor corneas were transplanted into Lewis recipients. High-risk transplantation meant that the transplants were sutured into the recipient beds with corneal neovascularization induced by placing three interrupted sutures in the host cornea. All of the recipients were divided in blinded fashion into four groups. Group I was injected with saline buffer. Group II was injected intraperitoneally with 0.2 mL SEB (75 microg/kg) at 4-day intervals on three occasions before transplantation. Group III was injected with 0.1 mL IL-1ra (1 mg/mL) subconjunctivally from the first day after transplantation for 2 weeks. Group IV received both SEB and IL-1ra. All transplants were evaluated for signs of rejection for 4 weeks after surgery. Ten days after transplantation, two recipients in each group were sacrificed for histopathological and immunological evaluation.

RESULTS

The mean survival time of the allografts in the control group was 5.89 +/- 0.79 days; in SEB group, 10.70 +/- 2.52 days; in IL-1ra group, 8.25 +/- 0.71 days; in the SEB and IL-1ra group, 17.36 +/- 2.39 days. CD4+ and CD8+ lymphocyte infiltration into the allografts and the percentage of the lymphocytes in the spleen and mandibular lymphatic nodes was significantly decreased among the treated groups with dampened lymphocyte reactivity. The SEB plus IL-1ra combination group showed the strongest inhibition.

CONCLUSION

SEB and IL-1ra are most effective in combination to treat high-risk corneal transplants.

The duration of in vitro stimulation with recall antigens determines the subset distribution of interferon-γ-producing lymphoid cells: A kinetic analysis using the Interferon-γ Secretion Assay™

Analyses of cellular immune responses during natural infections and following vaccination with established or candidate vaccines are becoming increasingly important and so are the research tools used to achieve this goal. During a recent evaluation of the analytical performance characteristics of one of these techniques, the interferon-gamma secretion assay, we noticed that following overnight incubation of PBMC with recall antigens (varicella-zoster antigen, Candida albicans antigen or hepatitis B surface antigen) NK cells are frequently the most predominant interferon-gamma-producing cell population. In this study, we monitored the subset distribution of interferon-gamma-producing cells following more extended in vitro culture periods and found that, irrespective of the antigen applied, the contribution of NK cells decreased whereas the importance of T cells and NKT cells rose. Analysis of the subset distribution showed that HBsAg stimulated CD4 cells predominantly whereas Candida antigen and varicella-zoster antigen were better inducers of CD8 responses. No correlation was found between the kinetics of total number of interferon-gamma-producing cells and the changes of concentrations of interferon-gamma in the culture supernatants. Interferon-gamma levels in culture supernatants correlated strongly with the kinetics of T(H) lymphocytes (CD3+, CD4+), CTL (CD3+, CD8+), and NKT cells (CD3+, CD56+). These observations lead us to conclude that methods that enumerate cytokine-secreting cells without determining their phenotype should be interpreted with great care and that an 'elispot' should not be directly considered as the footprint of a T lymphocyte.

Non-specific tolerance induced by staphylococcal enterotoxin B in treating high risk corneal transplantation in rats

AIMS

To explore the role of staphylococcal enterotoxin B (SEB) in treating high risk corneal keratoplasty in rats.

METHODS

Rat corneal high risk transplantation rejection models were set up using Fisher 344 and Lewis rats. The experimental rats were injected intraperitoneally with 0.2 ml SEB at different concentrations before keratoplasty. The rejection indexes of the allograft were recorded and the lymphocyte infiltration in the allograft and the percentage of the lymphocyte subpopulation in the lymphatic organs were also examined. Lymphocyte proliferation ability and the concentration of IL-2 and IL-10 in the serum were also evaluated.

RESULTS

Compared with the control group, SEB prolonged the survival time of the allograft significantly from 7 to 12 days. It could also reduce CD4(+) and CD8(+) lymphocyte infiltration in the allograft and minimise the percentage of CD4(+) and CD8(+) lymphocytes in the lymphatic organs. The lymphocyte proliferation ability was also weakened. However, the percentage of CD4(+) NK T lymphocytes in the lymphatic organs was raised. The serum concentration of IL-10 was higher but IL-2 was lower in the SEB treated groups.

CONCLUSIONS

SEB prolonged the survival time of the allograft in high risk rat corneal allo-transplantation, which may be caused by T cell deletion and acquisition of non-specific tolerance.

Frequency of proteinase 3 (PR3)-specific autoreactive T cells determined by cytokine flow cytometry in Wegener's granulomatosis

OBJECTIVE

Previous studies have shown proliferation to Wegener's autoantigen, proteinase 3 (PR3). We tested immunogenicity of PR3-derived peptides and determined frequencies of PR3-specific T cells using cytokine flow cytometry in Wegener's granulomatois (WG).

METHODS

Peripheral blood T-cell responses were measured after stimulation with previously described PR3-derived peptides. PBMC were stimulated with PR3-derived peptides or control stimuli for up to 10 days. Cells were stained with antibodies against CD4 or CD8, CD69 and intracellular TNF-alpha and analyzed by flow cytometry. PR3-specific T cells were counted as the percentage of CD69(+)TNF-alpha(+)double positive T cells after stimulation.

RESULTS

Frequencies of PR3-specific peripheral blood T cells after short-term stimulation (<or=0.4%) were lower compared to frequencies of PR3-specific CD4(+)T cells (0.64+/-0.09%, mean+/-SEM) and PR3-specific CD8(+)T cells (0.65+/-0.18%) after 10 days of stimulation in WG. There were no differences of the frequency of PR3-specific T cells between WG and healthy controls after stimulation with other peptides. The frequency of PR3-specific CD8(+)T cells stimulated with a preferentially HLA-A*0201 binding PR3-peptide sequence was higher compared to the frequency of T cells stimulated with a HLA-B*0702 binding PR3-peptide in one WG patient whose HLA type was known (A2B7).

CONCLUSION

Low frequencies of TNF-alpha(+)PR3-specific T cells can be detected in individual WG patients and controls using cytokine flow cytometry. The pattern and time course of cytokine production in response to PR3 peptides needs to be further elucidated. Additional factors such as the influence of proinflammatory or regulatory T cells might be important for the induction of autoimmunity in WG.