HLA-B27 transgenic rats and strains of HLA-B27-transgenic beta(2)-microglobulin (beta(2)m)-deficient mice develop a multisystem inflammatory disease affecting the joints, skin, and bowel with strong ...similarity to human spondyloarthritis. We show that HLA-B27 transgenic mice and rats express HC10-reactive, beta(2)m-free HLA-B27 homodimers (B27(2)) and multimers, both intracellularly and at the cell surface of leukocytes, including rat dendritic cells. Fluorescent-labeled tetrameric complexes of HLA-B27 homodimers (B27(2) tetramers) bind to populations of lymphocytes, monocytes, and dendritic cells. The murine (and probably rat) paired Ig-like receptors (PIRs) are ligands for B27(2). Thus, B27(2) tetramers stain RBL cells transfected with murine activating PIR-A4 and inhibitory PIR-B receptors. Murine PIR-A and -B can be immunoprecipitated from the RAW264.7 macrophage cell line, and murine PIR-A can be immunoprecipitated from the J774.A1 line using B27(2). B27(2) tetramer staining corresponds to the distribution of PIR expression on lymphoid and myeloid cells and on murine macrophage cell lines. B27(2) can induce TNF-alpha release from the J774.A1 macrophage cell line. The binding of B27(2) to PIR is inhibited by HC10, an mAb that ameliorates arthritis in HLA-B27(+) beta(2)m(-/-) mice. The expression and PIR recognition of B27(2) could explain the pathogenesis of rodent spondyloarthritis.
Public policy requires public support, which in turn implies a need to enable the public not just to understand policy but also to be engaged in its development. Where complex science and technology ...issues are involved in policy making, this takes time, so it is important to identify emerging issues of this type and prepare engagement plans. In our horizon scanning exercise, we used a modified Delphi technique. A wide group of people with interests in the science and policy interface (drawn from policy makers, policy adviser, practitioners, the private sector and academics) elicited a long list of emergent policy issues in which science and technology would feature strongly and which would also necessitate public engagement as policies are developed. This was then refined to a short list of top priorities for policy makers. Thirty issues were identified within broad areas of business and technology; energy and environment; government, politics and education; health, healthcare, population and aging; information, communication, infrastructure and transport; and public safety and national security.
The presence of an anti‐bacterial T cell response and evidence of bacterial products in inflamed joints of reactive arthritis patients suggests an antigen transportation role in this disease for ...macrophages and dendritic cells. We have investigated the functional properties and in vivo migration of macrophages and DC after infection with Salmonella enterica serovar Typhimurium (S. typhimurium). BM‐derived macrophages and DC displayed enhanced expression of costimulatory molecules (CD40 and CD86) and increased production of pro‐inflammatory cytokines (TNF‐alpha, IL‐6 and IL‐12p40) and nitric oxide after infection. Upon adoptive transfer into mice, infected DC migrated to lymphoid tissues and induced an anti‐Salmonella T cell response, whereas infected macrophages did not. Infection of DC with S. typhimurium was associated with strong up‐regulation of the chemokine receptor CCR7 and acquisition of responsiveness to chemokines acting through this receptor. Moreover, S. typhimurium‐infected CCR7‐deficient DC were unable to migrate to lymph nodes after adoptive transfer, although they did reach the spleen. Our data demonstrate distinct roles for macrophages and DC as antigen transporters after S. typhimurium infection and a dependence on CCR7 for migration of DC to lymph nodes after bacterial infection.
The strong association of HLA B27 with spondyloarthropathies contrasts strikingly with most autoimmune diseases, which are HLA class II associated and thought to be mediated by CD4+ T lymphocytes. By ...introducing a human-derived HLA B27-restricted TCR into HLA B27 transgenic mice, we have obtained a functional TCR transgenic model, GRb, dependent on HLA B27 for response. Surprisingly, HLA B27 supported CD4+ as well as CD8+ T cell responses in vivo and in vitro. Further, HLA B27-restricted CD4+ T cells were capable of differentiation into a range of Th1 and Th2 T cell subsets with normal patterns of cytokine expression. The transgenic T cells were also able to enhance clearance of recombinant vaccinia virus containing influenza nucleoprotein in vivo. This is the first description of a human HLA class I-restricted TCR transgenic line. The existence of CD4+ MHC class I-restricted T cells has significant implications for immune regulation in autoimmunity and, in particular, in HLA B27-associated arthritis. We believe that this model provides a novel system for the study of unusual T cell behavior in vivo.
Summary
The human major histocompatibility complex (MHC) class I allele HLA‐B27 is strongly associated with seronegative spondyloarthropathies including ankylosing spondylitis and reactive arthritis. ...Although of unknown aetiology, one hypothesis suggests that a cytotoxic T cell (CTL) response against a self‐antigen at sites of inflammation, such as entheses or joints may be involved. The chondrocyte is one of the major specialized cell types found both in articular cartilage and cartilaginous entheses and therefore is a possible source of such an antigen. CTL recognition of these cells is a potential mechanism for inflammation and cartilage damage, both through direct lysis of chondrocytes and the secretion of pro‐inflammatory cytokines such as tumour necrosis factor and interferon‐γ (IFN‐γ). We test the feasibility of this hypothesis by examining the ability of chondrocytes to present antigen to CTL in vitro. Chondrocytes isolated from the ribcages of mice did not constitutively express detectable levels of MHC class I by fluorescence‐activated cell sorting analysis. In addition, they were resistant to lysis by alloreactive and influenza A virus nucleoprotein (NP)‐specific CTL. However, treatment of chondrocytes with IFN‐γ up‐regulated MHC class I expression and rendered the cells susceptible to lysis by CTL. Similarly, IFN‐γ‐treated chondrocytes infected with influenza A virus were recognized by NP‐specific CTL, though with variable efficiency. Thus, we suggest that under certain circumstances CTL‐mediated lysis of chondrocytes is potentially a potent mechanism for cartilage damage in vivo, but that low levels of MHC class I on healthy chondrocytes protects from immune recognition in health.
The association of HLA-B27 with certain forms of arthritis implies a role for MHC class I-restricted T cells in the arthritic process. Our aim was to study CD8+ T cell responses towards specific ...antigens localized in joint tissue. Known determinants were introduced into chondrocytes of transgenic (TG) mice, under the control of the cis-regulatory sequences of the human type II collagen gene (COL2A1). Two Escherichia coli β-galactosidase (β-gal)-expressing lines were derived (CIIL73 and CIIL64) as well as two lines (CIINP) expressing influenza A virus nucleoprotein (NP). Expression of the antigens could be demonstrated in cartilaginous tissues. The TG lines showed variable degrees of responsiveness towards the transgene-introduced antigens; whilst 75% of CIIL73 mice had an impaired cytotoxic T lymphocyte (CTL) response towards β-gal, the response in CIIL64 mice was essentially normal. However, both lines displayed normal proliferative and antibody responses to β-gal. A reduced CTL response was seen to NP in the CIINP lines in ~65% of the animals. In spite of the persistence of T cell responses to the transgene antigens in these lines, induction of CTL responses alone has so far failed to induce clinical signs of arthritis. Interestingly, some animals expressing β-gal were susceptible to arthritis following challenge with type II collagen alone, whilst their non-TG littermates and TG mice from other lines remained unaffected. As β-gal is expressed by E. coli, a component of the normal gut flora, this suggests a possible role for gut-derived immune responses. We believe these lines could form the basis of a model for studying links between intestinal inflammation and arthritis.
The presence of potentially autoreactive T cells is a necessary, but not sufficient, condition for the development of autoimmune disease. However, the relationship between T cell response and ...susceptibility to disease is not straightforward. In this report, we use experimental allergic encephalomyelitis as a model to demonstrate that subtle alterations of the T cell response to an encephalitogenic epitope are sufficient to cause a dramatic decrease in disease susceptibility. Transgenic expression of a fusion protein of hen egg lysozyme and an encephalitogenic peptide of myelin basic protein (MBP) residues 84-105, coexpressed with MHC class II, causes profound tolerance to hen egg lysozyme, while maintaining a near normal response to MBP. Detailed analysis of the T cell repertoire of transgenic animals using a panel of T cell hybridomas revealed a highly selective loss of one minor component of the response to the MBP84-104 region. Despite this, transgenic animals were highly resistant to experimental allergic encephalomyelitis induction with the MBP peptide, indicating that minor changes to the T cell repertoire may result in major alterations in disease susceptibility. Possible reasons for this are discussed.
Cytotoxic T lymphocytes (CTL) recognize protein antigens which have been processed by the target cell and then presented in association with the relevant class I molecule of the major ...histocompatibility complex (MHC). Short synthetic peptides, which are able to associate directly with target cells, may substitute for these processed fragments in stimulating antigen-specific CTL responses. Using this approach, a dominant HLA-A2-restricted epitope has previously been mapped to residues 58-68 of influenza A virus matrix protein. Here we report HLA-A2-restricted CTL which are also able to recognize this short synthetic peptide in association with HLA-Aw69, but which fail to recognize HLA-Aw69 expressing cells infected with influenza A virus. Furthermore, individuals possessing HLA-Aw69 who respond to influenza A virus, do not respond to M58-68. These results imply that the low response to this epitope on infection of HLA-Aw69 individuals with influenza A is due to failure of the naturally processed product of matrix protein to associate with Aw69.
A previously identified Kd restricted epitope of influenza A virus nucleoprotein (147-161) was modified, resulting in recognition by Kd restricted cytotoxic T cells at significantly lower ...concentrations than the natural peptide sequence. This was achieved by first refining the epitope to the minimum determinant 147-158. Deletion of arginine 156 resulted in a peptide that was shown to be greatly superior in both dose response titrations and in its rate of association with cells to form targets. Analog peptides were tested to determine the important amino acid changes. These data suggest that T cell epitopes can be modified to result in improved immunological recognition.
The invariant chain (li) binds nascent major histocompatibility complex (MHC) class II molecules, blocking peptide binding until the complex dissociates in the endosomes. This may serve to ...differentiate the MHC class I and II antigen presentation pathways and enable class II molecules to efficiently bind peptides in the endosomes. This hypothesis was addressed by probing spleen cells from a combination of knock-out and transgenic mice with a large panel of T cell hybridomas. The li molecule blocked the presentation of a range of endogenously synthesized epitopes, but some epitopes actually required li. Thus, the influence of li on presentation does not follow simple rules. In addition, mice expressing li were not tolerant to epitopes unmasked in its absence, a finding with possible implications for autoimmunity.
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