Stimulation of synovial fluid mononuclear cells with the human 65-kD heat shock protein or with live enterobacteria leads to preferential expansion of TCR-gamma delta+ lymphocytes

γδ T cell IFNγ production is directly subverted by Yersinia pseudotuberculosis outer protein YopJ in mice and humans

Yersinia pseudotuberculosis is a foodborne pathogen that subverts immune function by translocation of Yersinia outer protein (Yop) effectors into host cells. As adaptive γδ T cells protect the intestinal mucosa from pathogen invasion, we assessed whether Y. pseudotuberculosis subverts these cells in mice and humans. Tracking Yop translocation revealed that the preferential delivery of Yop effectors directly into murine Vγ4 and human Vδ2⁺ T cells inhibited anti-microbial IFNγ production. Subversion was mediated by the adhesin YadA, injectisome component YopB, and translocated YopJ effector. A broad anti-pathogen gene signature and STAT4 phosphorylation levels were inhibited by translocated YopJ. Thus, Y. pseudotuberculosis attachment and translocation of YopJ directly into adaptive γδ T cells is a major mechanism of immune subversion in mice and humans. This study uncovered a conserved Y. pseudotuberculosis pathway that subverts adaptive γδ T cell function to promote pathogenicity.

Unconventional γδ T cells are a dynamic immune population important for mucosal protection of the intestine against invading pathogens. We determined that the foodborne pathogen Y. pseudotuberculosis preferentially targets an adaptive subset of these cells to subvert immune function. We found that direct injection of Yersinia outer proteins (Yop) into adaptive γδ T cells inhibited their anti-pathogen functions. We screened all Yop effectors and identified YopJ as the sole effector to inhibit adaptive γδ T cell production of IFNγ. We determined that adaptive γδ T cell subversion occurred by limiting activation of the transcription factor STAT4. When we infected mice with Y. pseudotuberculosis expressing an inactive YopJ, this enhanced the adaptive γδ T cell response and led to greater cytokine production from this subset of cells to aid mouse recovery. This mechanism of immune evasion appears conserved in humans as direct injection of Y. pseudotuberculosis YopJ into human γδ T cells inhibited cytokine production. This suggested to us that Y. pseudotuberculosis actively inhibits the adaptive γδ T cell response through YopJ as a mechanism to evade immune surveillance at the site of pathogen invasion.

The danger model approach to the pathogenesis of the rheumatic diseases

The danger model was proposed by Polly Matzinger as complement to the traditional self-non-self- (SNS-) model to explain the immunoreactivity. The danger model proposes a central role of the tissular cells' discomfort as an element to prime the immune response processes in opposition to the traditional SNS-model where foreignness is a prerequisite. However recent insights in the proteomics of diverse tissular cells have revealed that under stressful conditions they have a significant potential to initiate, coordinate, and perpetuate autoimmune processes, in many cases, ruling over the adaptive immune response cells; this ruling potential can also be confirmed by observations in several genetically manipulated animal models. Here, we review the pathogenesis of rheumatic diseases such as systemic lupus erythematous, rheumatoid arthritis, spondyloarthritis including ankylosing spondylitis, psoriasis, and Crohn's disease and provide realistic approaches based on the logic of the danger model. We assume that tissular dysfunction is a prerequisite for chronic autoimmunity and propose two genetically conferred hypothetical roles for the tissular cells causing the disease: (A) the Impaired cell and (B) the paranoid cell. Both roles are not mutually exclusive. Some examples in human disease and in animal models are provided based on current evidence.

Synergistic effects of ethanol and isopentenyl pyrophosphate on expansion of γδ T cells in synovial fluid from patients with arthritis

Low to moderate ethanol consumption has been associated with protective effects in autoimmune diseases such as rheumatoid arthritis, RA. An expansion of γδ T cells induced by isopentenyl pyrophosphate, IPP, likewise seems to have a protective role in arthritis. The aim of this project was to test the hypothesis that low doses of ethanol can enhance IPP-induced expansion of synovial fluid γδ T cells from patients with arthritis and may thereby potentially account for the beneficial effects of ethanol on symptoms of the arthritic process. Thus, mononuclear cells from synovial fluid (SF) from 15 patients with arthritis and from peripheral blood (PB) from 15 healthy donors were stimulated with low concentrations of ethanol and IPP for 7 days in vitro. IPP in combination with ethanol 0.015%, 2.5 mM, equivalent to the decrease per hour in blood ethanol concentration due to metabolism, gave a significantly higher fractional expansion of SF γδ T cells compared with IPP alone after 7 days (ratio 10.1+/-4.0, p<0.0008, n = 12) in patients with arthritis. Similar results were obtained for PB γδ T cells from healthy controls (ratio 2.0+/-0.4, p<0.011, n = 15). The augmented expansion of γδ T cells in SF is explained by a higher proliferation (p = 0.0034, n = 11) and an increased survival (p<0.005, n = 11) in SF cultures stimulated with IPP plus ethanol compared to IPP alone. The synergistic effects of IPP and ethanol indicate a possible allosteric effect of ethanol. Similar effects could be seen when stimulating PB with ethanol in presence of risedronate, which has the ability to increase endogenous levels of IPP. We conclude that expansion of γδ T cells by combinatorial drug effects, possibly in fixed-dose combination, FDC, of ethanol in the presence of IPP might give a protective role in diseases such as arthritis.

Antigens in tea-beverage prime human Vgamma 2Vdelta 2 T cells in vitro and in vivo for memory and nonmemory antibacterial cytokine responses

Human gammadelta T cells mediate innate immunity to microbes via T cell receptor-dependent recognition of unprocessed antigens with conserved molecular patterns. These nonpeptide alkylamine antigens are shared by tumor cells, bacteria, parasites, and fungi but also by edible plant products such as tea, apples, mushrooms, and wine. Here we show that priming of gammadelta T cells with alkylamine antigens in vitro results in a memory response to these antigens. Such priming results also in a nonmemory response to whole bacteria and to lipopolysaccharide, characterized by IL-12-dependent secretion of IFN-gamma by gammadelta T cells and by gammadelta T cell proliferation. Drinking tea, which contains l-theanine, a precursor of the nonpeptide antigen ethylamine, primed peripheral blood gammadelta T cells to mediate a memory response on reexposure to ethylamine and to secrete IFN-gamma in response to bacteria. This unique combination of innate immune response and immunologic memory shows that gammadelta T cells can function as a bridge between innate and acquired immunity. In addition, these data provide an explanation for the health benefits of tea.

Structure of gammadelta T cell receptors and their recognition of non-peptide antigens

The gammadelta T cell receptors (TCRs) and alphabeta TCRs are similar in both sequence and structure; however, gammadelta+ and alphabeta+ T cells are not merely similar lymphocytes with subtly different receptors. These cell types differ in several ways, including the types of antigens recognized, the mechanism of antigen presentation and recognition and the mechanism and kinetics of downstream signaling events. gammadelta TCRs can directly recognize antigens in the form of intact proteins or non-peptidic compounds, unlike alphabeta TCRs which recognize peptide antigens bound to major histocompatibility complex molecules (MHC). One of the major classes of human gammadelta+ T cells expresses Vgamma9Vdelta2 TCRs which recognize pyrophosphomonoester, alkylamine and aminobisphosphonate antigens. This review focuses on the recently determined structure of a Vgamma9Vdelta2 TCR, with emphasis on antigen recognition and receptor signaling.

Antibacterial effect of human V gamma 2V delta 2 T cells in vivo

V gamma 2V delta 2 cells, a class of T cells found only in primates, are reactive to nonpeptide organophosphate and alkylamine antigens secreted by bacteria and parasites. These cells make up 2-5% percent of human peripheral blood T cells but expand to make up 8-60% of peripheral blood T cells during bacterial and parasitic infections. We show here, using a chimeric severe combined immunodeficiency (SCID) mouse (hu-SCID) model, that human V gamma 2V delta 2 T cells mediate resistance to extracellular gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli and Morganella morganii) bacteria, as assessed by survival, body weight, bacterial loads, and histopathology. Surprisingly, this bacterial resistance was evident 1 day after infection, and bacteria were cleared well before gamma delta T cell expansion was detected 6 days after infection. Decreased resistance in V delta 2 T cell-depleted hu-SCID mice correlated with decreased serum IFN-gamma titers. Intravenous treatment of infected, reconstituted hu-SCID mice with pamidronate, a human V gamma 2V delta 2 T cell-specific aminobisphosphonate antigen, markedly increased the in vivo antibacterial effect of V gamma 2V delta 2 T cells. Therefore, this large pool of antigen-specific, yet immediately reactive memory human V gamma 2V delta 2 T cells is likely to be an important mediator of resistance against extracellular bacterial infection and may bridge the gap between innate and acquired immunity.

Human gamma delta T cells recognize alkylamines derived from microbes, edible plants, and tea: implications for innate immunity

Approximately 4% of peripheral blood T cells in humans express a T cell receptor with markedly restricted germline gene segment usage (V gamma 2 V delta 2). Remarkably, these T cells expand 2- to 10-fold (8%-60% of all circulating T cells) during many microbial infections. We show here that these T cells recognize a family of naturally occurring primary alkylamines in a TCR-dependent manner. These antigenic alkylamines are secreted to millimolar concentrations in bacterial supernatants and are found in certain edible plants. Given the large numbers of memory V gamma 2 V delta 2 T cells in adult humans, recognition of alkylamine antigens offers the immune system a response of the magnitude of major superantigens for alpha beta T cells and may bridge the gap between innate and adaptive immunity.

Role of heat shock proteins in protection from and pathogenesis of infectious diseases

Increased synthesis of heat shock proteins (hsp) occurs in prokaryotic and eukaryotic cells when they are exposed to stress. By increasing their hsp content, cells protect themselves from lethal assaults, primarily because hsp interfere with the uncontrolled protein unfolding that occurs under stress. However, hsp are not produced only by stressed cells; some hsp are synthesized constitutively and perform important housekeeping functions. Accordingly, hsp are involved in the assembly of molecules which play important roles in the immune system. It is not surprising that due to their wide distribution and their homology among different species, hsp represent target antigens of the immune response. Frequent confrontation of the immune system with conserved regions of hsp which are shared by various microbial pathogens can potentiate antimicrobial immunity. However, long-term confrontation of the immune system with hsp antigens which are similar in the host and invaders may convert the immune response against these host antigens and promote autoimmune disease. This review provides an overview of the role of hsp in immunity with a focus on infectious and autoimmune diseases.

Stress protein-induced immunosuppression: inhibition of cellular immune effector functions following overexpression of haem oxygenase (HSP 32)

This is the first report on suppression of immune effector functions following upregulation of heat shock protein 32 (HSP 32), known as haem oxygenase (HO-1). Here we evaluated the effect of cobalt-protoporphyrin (CoPP)-induced HO-1 expression on cell-mediated immune responses. Administration of CoPP to CBA mice resulted in overexpression of HO-1 in the spleen, liver and kidneys. In vitro measurements of T cell-mediated and NK-cell-mediated cytotoxicity in spleens from CoPP-treated animals demonstrated a severe suppression of their effector functions while administration of Zn-PP or vitamin B12 had no effect. Furthermore, CoPP therapy decreased the lymphoproliferative alloresponse and differentiation of cytotoxic T cells. Inhibition of proliferation appeared to be due to cell growth arrest with an increased number of cells staying in G0/G1 phase. Despite the suppressed proliferative response, IL-2 production in the MLR was not inhibited. In contrast, CoPP decreased the production of IL-10, IFN-gamma and TNF-alpha. In vivo, CoPP prolonged the survival of heterotopic heart allografts in mice. The immunosuppressive effects following CoPP-mediated upregulation of HO-1 were similar to those observed after peptide-mediated upregulation of HO-1. The results indicate that overexpression of HO results in the inhibition of several immune effector functions and thus provides an explanation for stress-induced immunosuppression.

Gammadelta+ and CD4+ alphabeta+ human T cell subset responses upon stimulation with various Mycobacterium tuberculosis soluble extracts

By using a flow cytometric technique which allows direct identification of proliferating cells within mixed cell populations, we have previously described that soluble extracts obtained from Mycobacterium tuberculosis or M. avium represent strong stimuli for human gammadelta+ T cells. In the present study, we demonstrate that the protocol used for the preparation of M. tuberculosis soluble extracts may have an impact on their gammadelta+ T cell stimulatory capacity. In agreement with our previous data, soluble extracts prepared from bacteria killed at 85 degrees C and directly disrupted by prolonged sonication (TBe), elicited a strong proliferation of gammadelta+ T cells after 6-7 days of stimulation. In contrast, when soluble extracts were obtained from bacteria autoclaved (121 degrees C, 25 min) and then washed by centrifugation, a predominant proportion of CD4+ alphabeta+ T cells was achieved in the responding population. The stimulatory activity for gammadelta+ T cells was recovered in the supernatant of the autoclaved bacteria, indicating that autoclaving of M. tuberculosis bacilli releases an antigen(s) into the supernatant which stimulates human gammadelta+ T cells. While protease digestion of TBe only partially reduced its stimulatory capacity on gammadelta+ T cells, the stimulatory component(s) released into the supernatant after autoclavation of bacilli was found to be sensitive to protease digestion. Interestingly, in contrast to the preponderant proportion of gammadelta+ T cells induced in the responding population by unfractionated TBe, when the extract was fractionated by fast performance liquid chromatography (FPLC), most of the fractions exhibited a strong stimulatory capacity on CD4+ alphabeta+ T cells only. The gammadelta+ T cell stimulatory activity was confined to the low molecular weight range FPLC fractions. Such results may suggest a possible regulatory role of gammadelta+ T cells on CD4+ alphabeta+ T cells.

Human gamma delta T-cell recognition of Yersinia enterocolitica

We have studied the human gamma delta T-cell response to Yersinia enterocolitica, a facultative intracellular bacterium which causes gastroenteritis and, particularly in human leucocyte antigen (HLA)-B27+ individuals, reactive arthritis (ReA). A marked proliferation of that cytotoxic gamma delta T cells is seen when Yersinia-infected lymphoblastoid cell lines or fixed intact Yersinia are added to cultures of mononuclear cells derived from the synovial fluid of ReA patients or from the peripheral blood of healthy donors. In contrast, heat-inactivated Yersinia fail to stimulate the gamma delta T-cell response. The gamma delta T-cell lines generated killed both autologous and allogeneic infected cell lines. Interestingly, a T-cell line generated from synovial fluid mononuclear cells (SFMC) killed infected autologous cell lines and a cell line matched for HLA-B27 less well than infected allogeneic target cells. gamma delta T-cell clones isolated from this line were found to express V gamma 9V delta 2 T-cell receptor (TCR) and also killed infected mismatched cells more efficiently than autologous targets. Moreover, from experiments using major histocompatability complex (MHC)-deficient cell lines, it was apparent that target cell recognition was MHC independent. Our results suggest that gamma delta T cells can be involved in immunity to Yersinia enterocolitica and should be taken into account when considering immunopathological mechanisms leading to reactive arthritis.

Aetiological agents and immune mechanisms in enterogenic reactive arthritis

Reactive arthritis is triggered by an infection, either of the genitourinary or gastrointestinal tracts; the common triggering bacteria in enteric ReA include salmonella, shigella, yersinia, and campylobacter. It is still not clear how such different bacteria can lead to a similar clinical picture and have a similar association with the MHC class I antigen HLA-B27. Common both to enterogenic and urogenic bacteria is the type of peripheral joint involvement. However, this is not so different from other bacteria-associated arthritides and is probably the consequence of bacteria persistent inside the joint. What is unique to these bacteria is the HLA-B27-association and the nearly exclusively B27-linked clinical manifestations as sacroiliitis and iritis. Shigella-induced ReA has the highest B27-association while in salmonella- and chlamydia-induced ReA a lower association can be found. Mucosal entry of enterogenic bacteria give easy access to macrophages which might be important for the transport into the joint. Although bacteria-specific antibodies are of diagnostic value, the humoral immune response does not explain the immunopathogenesis and MHC-association of this disease. Bacteria-specific T-cells have been constantly found in the synovial fluid from ReA patients and have been further analysed. The identification of immunodominant antigens of these bacteria is of great importance to understand the pathogenesis. Although an antigen shared by all bacteria has not been identified until now progress is being made in this field. We have also to consider the possibility that these bacteria are not only driving the immune response themselves but rather work as a trigger for autoimmunity.

Role of bacteria-specific T cells in the immunopathogenesis of reactive arthritis

Reactive arthritis is a usually self-limited sterile inflammation of joints that follows certain bacterial gastrointestinal or urogenital infections. The immunopathogenesis involves CD4+ T cells, which mediate an antigen-specific TH1 response to bacterial constituents within the joint. Properties of the arthritogenic bacteria and the physicochemical characteristics of the bacterial antigens may contribute to the development of reactive arthritis.

Differential effects of IL-10 on proliferation and cytokine production of human gamma/delta and alpha/beta T cells

Gamma/delta TCR bearing T lymphocytes represent a T-cell subset whose functional relevance remains unclear. Nevertheless these T cells may play a role in the early immune response against bacteria. Until now the regulatory mechanisms on this response have not been investigated. The study described here evaluated the immunoregulatory effects of Interleukin-10 on gamma/delta and alpha/beta TCR-positive T-cell clones and freshly isolated peripheral-blood mononuclear cells (PBMC). IL-10 has been shown previously to inhibit lectin and antigen-induced proliferation and cytokine production by alpha/beta T cells. The results outlined below show that rhIL-10 strongly inhibits lectin-induced production of IFN-gamma, TNF-alpha, IL-2, and to a lesser degree proliferation and IL-4 production of both T-cell subsets. As IL-10 did not inhibit proliferation but at the same time strongly suppressed cytokine production in various experiments, the hypothesis that it could function as a growth factor for human T cells as has been described for murine thymocytes was tested. The data demonstrate that, although the gamma/delta T-cell clones tested do not produce IL-10 they can use it as a growth factor in combination with IL-2, IL-4 or alone. Furthermore, IL-10 has the same properties on human alpha/beta T-cell clones and PBMC. In summary, it is shown that IL-10 has pleiotropic effects on gamma/delta and alpha/beta TCR+ T cells by inhibiting lectin-induced cytokine production and by acting as a growth factor for these cells alone or in combination with IL-2 or IL-4.

HLA-B27-restricted CD8 T cells derived from synovial fluids of patients with reactive arthritis and ankylosing spondylitis

Ankylosing spondylitis and seronegative spondylarthropathies such as Reiter's syndrome and reactive arthritis are strongly associated with HLA-B27. However, the mechanisms by which HLA-B27 is involved in disease susceptibility and pathogenesis are unknown. If the disease association is a consequence of HLA-B27's physiological function in antigen presentation, the disease should be mediated by cytotoxic T lymphocytes (CTLs) that recognise bacterial or self peptides presented by HLA-B27. Proof of this arthritogenic peptide model requires isolation of B27-restricted CD8 T cells from arthritic joints of patients with spondylarthropathies. An important question is whether "arthritogenic" bacteria such as yersinia or salmonella can generate HLA-B27-restricted bacteria-specific CTLs. We describe such HLA-B27-restricted CTLs. We tested a panel of 354 alpha beta-TCR CD8 T lymphocyte clones (TLCs) that had been derived from the synovial fluid of 4 patients with reactive arthritis and 2 patients with ankylosing spondylitis. In 1 patient with yersinia-induced arthritis, 2 TLCs were identified that killed specifically yersinia-infected B27 target cells. In another patient with salmonella-induced arthritis, 1 B27-restricted CD8 TLC that recognised both salmonella and yersinia was identified. In 5 of the 6 patients autoreactive CTLs were found, 5 of which showed B27-restricted killing of uninfected cell lines. B27-restricted CTLs with specificity for arthritogenic bacteria or autoantigens provide a missing link in the pathogenesis of the HLA-B27-associated spondylarthropathies.

T cells in reactive arthritis

T cells appear to play a major role in the development, maintenance and also resolution of reactive arthritis (ReA). Recent advances in understanding the processes involved in T cell activation now allow us to examine the peripheral blood and synovial fluid T cell responses to given "arthritogenic" microorganisms in terms of antigen specificity, epitope identification, cytokine secretion patterns, HLA restriction and the role of different T cell subsets in ReA. Peripheral blood bulk proliferation and limiting dilution studies provide evidence that the peripheral T cell response against arthritis-associated gram-negative bacteria is decreased in patients developing immunological sequelae such as ReA after gastrointestinal infection. Using clonal analysis of synovial fluid CD4+ T cells it has been shown that a polyclonal rather than an oligoclonal response to a variety of bacterial antigens is induced at the site of synovitis and that these CD4+ T cells produce a Th1-type of cytokine. 65 kD heat shock protein may represent one of the possible linkages of anti-infectious and autoimmune reactions. Furthermore, a spectrum of killer cells is present in the synovial fluid of patients with ReA. This spectrum of cytotoxic T cells includes antigen-specific, class I-restricted alpha beta-TCR+CD8+ lymphocytes, antigen-specific, apparently non-MHC-restricted alpha beta-TCR+CD8+ lymphocytes and gamma delta-TCR+ cells with braod cytolytic activity directed against bacteria-infected target cells. HLA-B27-restricted Yersinia- or Salmonella-specific synovial fluid CD8+ T cells may provide the missing link between genetic disposition (HLA-B27) and extra-articular infection with arthritogenic bacteria in these patients.

In vivo response of murine gamma delta T cells to a heat shock protein-derived peptide

Recent results suggested that a large subset of heat shock protein HSP-60 reactive peripheral lymphoid gamma delta T cells preexists in normal adult mice, all members of which respond to a single segment of this common HSP. However, the experimental evidence supporting this idea involved in vitro peptide responses of gamma delta T-cell hybridomas generated from unprimed spleen cells. Here, we report an attempt to elicit a gamma delta T-cell response in vivo by stimulation of adult C57BL/10 mice with HSP-60 or an HSP-60-derived peptide fragment comprising amino acids 180-196 of mycobacterial HSP-60. Whereas no gamma delta T-cell response was detectable in mice injected with the intact protein, stimulation with the peptide altered the reactive gamma delta T-cell population in vivo. These changes were detected among hybridomas generated with cells restimulated in vitro and included a large increase in hybridizable gamma delta T cells, a nearly maximal increase in the relative frequency of HSP-60-reactive cells, and structural changes in expressed T-cell receptors of HSP-60-reactive cells. Interestingly, we failed to elicit a detectable alpha beta T-cell response to the particular peptide stimulatory for gamma delta T cells, although at least three other HSP-60 epitopes were recognized. Our data show that normal gamma delta T cells can respond in vivo to small peptide antigens. The gamma delta T-cell response to the HSP-60-derived peptide studied here is apparently independent of antigen-specific alpha beta T-cell reactivity.