Transfer of the inflammatory disease of HLA-B27 transgenic rats by bone marrow engraftment.

Objective. The association of reactive arthritis (ReA) with HLA‐B27 and the presence of bacterial antigen in joints with ReA suggest that bacterial peptides might be presented by the HLA‐B27 molecule and thus stimulate CD8 T cells. This study was performed to investigate the B27‐restricted cytotoxic T lymphocyte (CTL) response to Chlamydia trachomatis, using the model of HLA‐B27 transgenic mice. Methods. CBA (H‐2k) mice homozygous for HLA‐B*2705 and human β2‐microglobulin expression were immunized with C trachomatis or with the chlamydial 57‐kd heat‐shock protein (hsp57) coupled to latex beads. Cytotoxicity of lymphocytes from in vivo—primed transgenic mice was tested against C trachomatis—infected targets. Blocking experiments were performed with monoclonal antibodies (MAb) against class I major histocompatibility complex molecules. Results. A Chlamydia‐specific lysis of both B27‐transfected and nontransfected target cells was observed. This response could be inhibited by anti‐B27 and anti‐H2 MAb. CTL from mice immunized with hsp57 were not able to lyse Chlamydia‐infected target cells, and Chlamydia‐specific CTL could not destroy targets loaded with hsp57. Conclusion. These results suggest the existence of at least 2 CTL populations in this mouse model: one recognizing peptide of bacteria‐infected cells restricted by HLA‐B*2705 and the other recognizing peptide of bacteria‐infected cells restricted by the murine H‐2Kk molecule. It does not appear that hsp57 is a major target for the CD8 T cell response directed against Chlamydia. This animal model opens the way for identifying bacterial epitopes presented by HLA‐B27, and might thus help to clarify the pathogenesis of B27‐associated diseases.

Section: Discussioncontrasting

confidence: 45%

mentioning

confidence: 99%

Recognition of chlamydial antigen by HLA‐B27‐restricted cytotoxic T cells in HLA‐B*2705 transgenic CBA (H‐2^k) mice

Kuon

Lauster

Böttcher

et al. 1997

“…In rats, expression of HLA-B27 outside the bone marrow compartment is not necessary for spontaneous development of inflammatory disease (30), and it remains unclear precisely what cell type (or types) are critical in humans. These studies raise the possibility that there are cell-specific differences in the effects of HLA-B27 and underscore the potential importance of macrophages and up-regulation of HLA class I expression.…”

Section: Discussionmentioning

confidence: 99%

HLA–B27 up‐regulation causes accumulation of misfolded heavy chains and correlates with the magnitude of the unfolded protein response in transgenic rats: Implications for the pathogenesis of spondylarthritis‐like disease

Turner¹,

DeLay²,

Bai³

et al. 2007

129

103

Objective. HLA-B27 is implicated in the pathogenesis of spondylarthritis (SpA), yet the molecular mechanisms are incompletely defined. HLA-B27 misfolding has been associated with endoplasmic reticulum stress and activation of the unfolded protein response (UPR) in macrophages from HLA-B27/human ␤ 2 -microglobulin-transgenic (B27-transgenic) rats. This study was performed to assess the mechanisms that drive activation of the HLA-B27-induced UPR and to determine whether splenocytes respond in a similar manner.Methods. Splenocytes were isolated and bone marrow macrophages were derived from B27-transgenic and wild-type rats. Cells were treated for up to 24 hours with cytokines that induce class I major histocompatibility complex expression. HLA-B27 expression and misfolding were assessed by real-time reverse transcription-polymerase chain reaction, flow cytometry, and immunoblotting. Activation of the UPR was measured by quantifying UPR target gene expression and X-box binding protein 1 messenger RNA (mRNA) splicing.Results. HLA-B27 mRNA up-regulation was accompanied by a dramatic increase in the accumulation of misfolded heavy chains and preceded robust activation of the UPR in macrophages. When macrophages were treated with various cytokines, the magnitude of the UPR correlated strongly with the degree of HLA-B27 up-regulation. In contrast, B27-transgenic splenocytes exhibited only low-level differences in the expression of UPR target genes after exposure to interferon-␥ or concanavalin A, which resulted in minimal HLA-B27 up-regulation.Conclusion. These results suggest that HLA-B27-associated activation of the UPR in macrophages is attributable to the accumulation of misfolded heavy chains, and that certain cell types may be more susceptible to the effects of HLA-B27 misfolding. Strategies that eliminate HLA-B27 up-regulation and/or the accumulation of misfolded heavy chains may be useful in evaluating the role of these events in the pathogenesis of SpA.HLA-B27, a class I major histocompatibility complex (MHC) allele, is a major predisposing factor for the development of ankylosing spondylitis and other spondylarthritides (SpA) (1). In many populations, Ͼ90% of patients with ankylosing spondylitis are HLA-B27 positive, compared with Ͻ10% of healthy controls, highlighting this as one of the strongest HLA disease associations. However, despite 3 decades of investigation, the molecular contribution of HLA-B27 to the pathogenesis of SpA remains incompletely defined.It was previously reported that HLA-B27/human ␤ 2 -microglobulin (Hu␤ 2 m)-transgenic (B27-transgenic) rats develop an SpA-like inflammatory disease with a phenotype that includes arthritis and colitis, whereas HLA-B7/Hu␤ 2 m-transgenic (B7-transgenic) rats re-

“…We used mouse mAb HC10 (IgG2a specific for HLA-B free heavy chains), B9.12.1 (IgG2a specific for folded HLA-A, -B, and -C), B1.23.2 (IgG2a specific for folded HLA-B and -C), BBM.1 (IgG2b specific for Hu␤ 2 m), and OX18 (IgG1 specific for rat MHC class I). Their references, production, and use have been previously described (9,22,28).…”

Section: Methodsmentioning

confidence: 99%

Additional human β₂‐microglobulin curbs HLA–B27 misfolding and promotes arthritis and spondylitis without colitis in male HLA–B27–transgenic rats

Tran¹,

Dorris²,

Satumtira³

et al. 2006

158

150

Objective. Ankylosing spondylitis and related spondylarthritides are associated with HLA-B27, and also with intestinal inflammation, by unknown mechanisms. The folded HLA-B27 molecule is a trimer of heavy chain, ␤ 2 -microglobulin (␤ 2 m), and short peptide. However, B27 heavy chain has an unusual propensity to misfold and trigger the unfolded protein response (UPR). This study was initiated to test the hypothesis that B27 misfolding plays a role in the pathogenesis of spondylarthritis.Methods. Rats with high transgene copy numbers of HLA-B27 heavy chain together with human ␤ 2 m (Hu␤ 2 m) spontaneously develop colitis, peripheral arthritis, and occasional spondylitis, and those with lower transgene copy numbers remain healthy. We crossed disease-prone and healthy HLA-B27/Hu␤ 2 mtransgenic rat lines with a healthy line, 283-2, carrying only the Hu␤ 2 m transgene. HLA-B27 assembly was assessed by pulse-chase analysis of B27 molecules, and UPR triggering was assessed by measuring BiP/Grp78 messenger RNA (mRNA) in splenic concanavalin A blasts. Surface expression of B27 and Hu␤ 2 m was determined by flow cytometry. Disease manifestations were identified by clinical observation, histology, and measurement of cytokine mRNA.Results. The extra Hu␤ 2 m from the 283-2 line significantly reduced B27 misfolding and UPR triggering. Unexpectedly, however, F 1 male offspring of the healthy 21-3 line crossed with the 283-2 line showed a high prevalence, severity, and duration of arthritis and spondylitis, in the absence of colitis. The arthropathy showed many features characteristic of human spondylarthritis.Conclusion. These results suggest that B27 misfolding is associated with intestinal inflammation, but that neither B27 misfolding nor intestinal inflammation is critical to the development of B27-associated arthropathy.The spondylarthritides are a group of inflammatory rheumatic diseases characterized by axial and peripheral arthropathy and a variety of extraarticular lesions (1). In the prototype of these disorders, ankylosing spondylitis (AS), there is inflammation in the spinal and sacroiliac joints and in ligamentous attachments that, in severe cases, leads to bony fusion. The pathogenesis of spondylarthritis is poorly understood. Two factors strongly associated with these conditions are intestinal inflammation and the major histocompatibility complex (MHC) class I gene HLA-B27.With regard to the association with intestinal inflammation, the prevalence of inflammatory bowel disease (IBD) (both Crohn's disease and ulcerative colitis) is increased in individuals with AS. An even higher prevalence of IBD is found in individuals with other forms of spondylarthritis (2), and endoscopic studies with biopsy have shown a prevalence of microscopic inflammatory bowel lesions in 60-70% of patients