Paradoxical Effects of Endoplasmic Reticulum Aminopeptidase 1 Deficiency on HLA-B27 and Its Role as an Epistatic Modifier in Experimental Spondyloarthritis.

OBJECTIVE: We undertook this study to examine the functional basis for epistasis between endoplasmic reticulum aminopeptidase 1 (ERAP1) and HLA-B27 in experimental spondyloarthritis (SpA). METHODS: ERAP1-knockout rats were created using genome editing and bred with HLA-B27/human ß2 -microglobulin-transgenic (HLA-B27-Tg) rats and HLA-B7-Tg rats. The effects of ERAP1 deficiency on HLA allotypes were determined using immunoprecipitation and immunoblotting, flow cytometry, allogeneic T cell proliferation assays, and gene expression analyses. Animals were examined for clinical features of disease, and tissue was assessed by histology. RESULTS: ERAP1 deficiency increased the ratio of folded to unfolded (ß2 m-free) HLA-B27 heavy chains, while having the opposite effect on HLA-B7. Furthermore, in rats with ERAP1 deficiency, HLA-B27 misfolding was reduced, while free HLA-B27 heavy chain dimers on the cell surface and monomers were increased. The effects of ERAP1 deficiency persisted during up-regulation of HLA-B27 and led to a reduction in endoplasmic reticulum stress. ERAP1 deficiency reduced the prevalence of arthritis in HLA-B27-Tg rats by two-thirds without reducing gastrointestinal inflammation. Dendritic cell abnormalities attributed to the presence of HLA-B27, including reduced allogeneic T cell stimulation and loss of CD103-positive/major histocompatibility complex class II-positive cells, were not rescued by ERAP1 deficiency, while excess Il23a up-regulation was mitigated. CONCLUSION: ERAP1 deficiency reduced HLA-B27 misfolding and improved folding while having opposing effects on HLA-B7. The finding that HLA-B27-Tg rats had partial protection against SpA in this study is consistent with genetic evidence that loss-of-function and/or reduced expression of ERAP1 reduces the risk of ankylosing spondylitis. Functional studies support the concept that the effects of ERAP1 on HLA-B27 and SpA may be a consequence of how peptides affect the biology of this allotype rather than their role as antigenic determinants.

Gender differences in patient journey to diagnosis and disease outcomes: results from the European Map of Axial Spondyloarthritis (EMAS).

INTRODUCTION/OBJECTIVES: To evaluate the journey to diagnosis, disease characteristics and burden of disease in male and female patients with axial spondyloarthritis (axSpA) across Europe. METHOD: Data from 2846 unselected patients participating in the European Map of Axial Spondyloarthritis (EMAS) study through an online survey (2017-2018) across 13 countries were analysed. Sociodemographic characteristics, lifestyle, diagnosis, disease characteristics and patient-reported outcomes (PROs) [disease activity -BASDAI (0-10), spinal stiffness (3-12), functional limitations (0-54) and psychological distress (GHQ-12)] were compared between males and females using chi-square (for categorical variables) and student t (for continuous variables) tests. RESULTS: In total, 1100 (38.7%) males and 1746 (61.3%) females participated in the EMAS. Compared with males, females reported considerable longer diagnostic delay (6.1 ± 7.4 vs 8.2 ± 8.9 years; p < 0.001), higher number of visits to physiotherapists (34.5% vs 49.5%; p < 0.001) and to osteopaths (13.3% vs 24.4%; p < 0.001) before being diagnosed and lower frequency of HLA-B27 carriership (80.2% vs 66.7%; p < 0.001). In addition, females reported higher degree of disease activity in all BASDAI aspects and greater psychological distress through GHQ-12 (4.4 ± 4.2 vs 5.3 ± 4.1; p < 0.001), as well as a greater use of alternative therapies. CONCLUSION: The patient journey to diagnosis of axSpA is much longer and arduous in females, which may be related to physician bias and lower frequency of HLA-B27 carriership. Regarding PROs, females experience higher disease activity and poorer psychological health compared with males. These results reflect specific unmet needs in females with axSpA needing particular attention. Key Points • Healthcare professionals' perception of axSpA as a predominantly male disease may introduce some bias during the diagnosis and management of the disease. However, evidence about male-female differences in axSpA is scarce. • EMAS results highlight how female axSpA patients report longer diagnostic delay and higher burden of the disease in a large sample of 2846 participants of 13 European countries. • Results reflect unmet needs of European female patients. Healthcare professionals should pay close attention in order to accurately diagnose and efficiently manage axSpA cases while further research should be developed on the cause of reported gender differences.

Treatment of Active Crohn's Disease With an Ordinary Food-based Diet That Replicates Exclusive Enteral Nutrition.

BACKGROUND & AIMS: Exclusive enteral nutrition (EEN) is the only established dietary treatment for Crohn's disease (CD), but its acceptability is limited. There is a need for novel dietary treatments for CD. METHODS: We evaluated the effects of an individualized food-based diet (CD-TREAT), with similar composition to EEN, on the gut microbiome, inflammation, and clinical response in a rat model, healthy adults, and children with relapsing CD. Twenty-five healthy adults randomly received EEN or CD-TREAT for 7 days, followed by a 14-day washout period, followed by the alternate diet. Fecal microbiome and metabolome were assessed before and after each diet. HLA-B7 and HLA-B27 transgenic rats with gut inflammation received EEN, CD-TREAT, or standard chow for 4 weeks. Fecal, luminal, and tissue microbiome, fecal metabolites, and gut inflammation were assessed. Five children with active CD activity received CD-TREAT and their clinical activity and calprotectin were evaluated after 8 weeks of treatment. RESULTS: For healthy adults, CD-TREAT was easier to comply with and more acceptable than EEN. CD-TREAT induced similar effects to EEN (EEN vs CD-TREAT) on fecal microbiome composition, metabolome, mean total sulfide (increase 133.0 ± 80.5 vs 54.3 ± 47.0 nmol/g), pH (increase 1.3 ± 0.5 vs 0.9 ± 0.6), and the short-chain fatty acids (µmol/g) acetate (decrease 27.4 ± 22.6 vs 21.6 ± 20.4), propionate (decrease 5.7 ± 7.8 vs 5.2 ± 7.9), and butyrate (decrease 7.0 ± 7.4 vs 10.2 ± 8.5). In the rat model, CD-TREAT and EEN produced similar changes in bacterial load (decrease 0.3 ± 0.3 log10 16S rRNA gene copies per gram), short-chain fatty acids, microbiome, and ileitis severity (mean histopathology score decreases of 1.25 for EEN [P = .015] and 1.0 for CD-TREAT [P = .044] vs chow). In children receiving CD-TREAT, 4 (80%) had a clinical response and 3 (60%) entered remission, with significant concurrent decreases in fecal calprotectin (mean decrease 918 ± 555 mg/kg; P = .002). CONCLUSION: CD-TREAT replicates EEN changes in the microbiome, decreases gut inflammation, is well tolerated, and is potentially effective in patients with active CD. ClinicalTrials.gov, numbers NCT02426567 and NCT03171246.

Pathogenesis of Psoriatic Arthritis.

Psoriatic arthritis (PsA) is a chronic inflammatory arthropathy involving synovial and entheseal structures, associated with psoriasis or similar conditions. The etiopathogenetic mechanisms underlying PsA remain unclarified. The most accredited hypothesis involves a complex interaction among genetic, environmental, and immunological factors. Environmental agents, particularly trauma, mechanical stress, and smoke have been cited as possible factors in triggering the disease in genetically predisposed subjects. Like other forms of spondyloarthropathies, PsA shows several genetic associations with the major histocompatibility complex (MHC) class I alleles located on chromosome 6p21.3, particularly the human leukocyte antigen (HLA)-B27 in axial phenotypes. Recent studies have demonstrated that the most common epigenetic mechanisms that regulate gene expression in PsA are represented by DNA methylation, parent of origin effect or genomic imprinting, expression or activity of epigenetic modifying enzymes, and RNA interference (RNAi) by microRNAs (miRNAs). The mechanisms underlying PsA pathogenesis activate the innate and adaptive immune system and overexpression of TNF associated with amplification of the IL-23/IL-17 axis. In recent years, more PsA susceptibility genes and epigenetic mechanisms have been identified. Advances in the knowledge of innate and adaptive immune mechanisms underlying PsA have contributed to a better understanding of the heterogeneous clinical expression of the disease and, thus, to therapy strategies. The complexity of the pathogenetic aspects involving multiple cytokines, cell lines, and molecules needs to be further investigated to advance personalized therapeutic strategies and to improve outcomes of patients affected by PsA.

Mortality in American Veterans with the HLA-B27 gene.

OBJECTIVE: To compare survival in American veterans with and without the HLA-B27 (B27) gene. METHODS: Mortality was evaluated in a national cohort of veterans with clinically available B27 test results between October 1, 1999, and December 31, 2011. The primary outcome was the mortality difference between B27-positive and B27-negative veterans, adjusted for age, sex, race, and diagnoses codes for diseases that may have influenced both B27 testing and mortality, including psoriasis, inflammatory bowel disease, spondyloarthritis (SpA), and other types of inflammatory arthritis. The secondary outcomes were the adjusted mortality HR for B27+ and B27- veterans, in subgroups with and without SpA. RESULTS: Among veterans with available B27 test results, 27,652 (84.7%) were B27- and 4978 (15.3%) were B27+. The mean followup time was 4.6 years. Mortality was higher in the B27+ group than in the B27- group (HR 1.15, 95% CI 1.03-1.27). Mortality was also higher in the B27+ subgroups with SpA (HR 1.35, 95% CI 1.06-1.72) and without SpA (HR 1.11, 95% CI 0.99-1.24), but the difference was significant only in the subgroup with SpA. CONCLUSION: B27 positivity was associated with an increased mortality rate in a cohort of veterans clinically selected for B27 testing, after adjustment for SpA. In the subgroup with SpA, the mortality rate was associated with B27 positivity, and in the subgroup without SpA, there was a nonsignificant association between B27+ and mortality.

Chemically defined diet alters the protective properties of fructo-oligosaccharides and isomalto-oligosaccharides in HLA-B27 transgenic rats.

Non-digestible oligosaccharides (NDO) were shown to reduce inflammation in experimental colitis, but it remains unclear whether microbiota changes mediate their colitis-modulating effects. This study assessed intestinal microbiota and intestinal inflammation after feeding chemically defined AIN-76A or rat chow diets, with or without supplementation with 8 g/kg body weight of fructo-oligosaccharides (FOS) or isomalto-oligosaccharides (IMO). The study used HLA-B27 transgenic rats, a validated model of inflammatory bowel disease (IBD), in a factorial design with 6 treatment groups. Intestinal inflammation and intestinal microbiota were analysed after 12 weeks of treatment. FOS and IMO reduced colitis in animals fed rat chow, but exhibited no anti-inflammatory effect when added to AIN-76A diets. Both NDO induced specific but divergent microbiota changes. Bifidobacteria and Enterobacteriaceae were stimulated by FOS, whereas copy numbers of Clostridium cluster IV were decreased. In addition, higher concentrations of total short-chain fatty acids (SCFA) were observed in cecal contents of rats on rat chow compared to the chemically defined diet. AIN-76A increased the relative proportions of propionate, iso-butyrate, valerate and iso-valerate irrespective of the oligosaccharide treatment. The SCFA composition, particularly the relative concentration of iso-butyrate, valerate and iso-valerate, was associated (P ≤ 0.004 and r ≥ 0.4) with increased colitis and IL-1 ß concentration of the cecal mucosa. This study demonstrated that the protective effects of fibres on colitis development depend on the diet. Although diets modified specific cecal microbiota, our study indicates that these changes were not associated with colitis reduction. Intestinal inflammation was positively correlated to protein fermentation and negatively correlated with carbohydrate fermentation in the large intestine.

Enigmatic question of early reactive arthritis disclosed after researches of mycoplasmas, Chlamydia trachomatis and enteropathogens following the holistic vision of human being.

An HLA-B27 genetic profile patient is fully investigated by molecular analyses after an anamnestic assessment of multi-site ecosystems, following the holistic vision of human being.VDRL and Widal-Wright (WWR) resulted positive, showing at Wright’s reaction a title of 1:40. Of all the enzymatic activities measured, only the ALP enzymatic pool activities showed a low increasing value of 297 U/L. Of all later acute phase proteins, Only C3 c protein value (127 mg/dL) and fibrinogen (376 mg/dL) were altered. Cultural and molecular oropharyngeal ecosystem investigation resulted significantly positive to Mycoplasmas(Mhand Uu) and Chlamydia trachomatis(Ct) together with a spread of saprophytic flora. From an accurate anamnesis, several and severe uro-genital clinical symptomatology emerged from birth until the beginning of rheumatologic symptomatologies that were confirmed by oldest Mh, Uu and Ctsilent chronic infections between these ecosystems. The molecular HPV research was negative, while the Thin prep pap-test was indicative of vaginosis and cellular reactive changes associated with inflammation. Parasitological research resulted positive for presence of 5-7 newly-formed G. lambliacysts for microscopic field, while digestibility test was positive for presence of several free fatty acid crystals. The remarkable presence of indigested meat fibre and several mucous dense filaments were observed. The pH value was 6.5, while blood faecal test was positive. The values observed were: ferritin 12 microg/L (10-120), total iron-binding capacity (TIBC) 310 &mgr;g/dL (300+-20), unsaturated iron-binding capacity (UIBC) 286 microg/dL (200-220) and iron seric level 24 microg/dL (60-130). Faecal research highlighted a very scarce presence of E. coli, resulting in 102 UFC/g of stool. Of all enteroinvasive pathogens, researched by molecular analyses, only Yersinia spp. was positive. After several specific cycles of antibiotic and antinflammatory therapies, the patient improved its general health condition considerably and showed almost complete regression of aching inguinal lymph node inflammation. In a picture of a worsening inflammatory process, produced by pathogens like Mycoplasmas, chronic silent or low grade inflammation atypical agents, in young HLA-B27 positive patient, VDRL test resulted positive. This value represents the first non-specific unique spy to reveal the precocious immunological signal in order to register the beginning of early innate immune system decay, keeping in mind that mycoplasmal and chlamydial infections are the triggering of cancer in patients genetically susceptible.

High-throughput screening of chemical libraries for modulators of gene promoter activity of HLA-B2705: environmental pathogenesis and therapeutics of ankylosing spondylitis.

OBJECTIVE: Ankylosing spondylitis (AS) is a highly heritable disease with HLA-B27 being the strongest susceptible gene. In order to survey the environmental triggers for arthritis development, we used a high-throughput technique to screen the effects of 12,264 chemicals on the HLA-B27 gene promoter. METHODS: Promoter reporter transfectants 293T-HLA-B27 and HeLa-HLA-B27 were tested using robotics with 12,264 chemicals. Chemicals that modulated HLA-B27 promoter activity > 150% or < 40% were selected for further evaluation of IC50/EC50 and cell viability. RESULTS: The primary screening using the 293T-HLA-B27 promoter reporter cell line yielded 5.1% hits that either suppressed (556 chemicals) or enhanced (68 chemicals) the HLA-B27 promoter activity. A secondary reconfirmation screening was carried out with these 624 candidates using HeLa-HLA-B27 promoter reporter cells under several different culture conditions. The yield of positive candidates was 130, of which 47 were derived from natural products. Based on the bio-information of those positive natural products, 21 chemicals were selected for analysis by dose-response IC50/EC50 experiments. Eight compounds showed potential pharmacological activities. Two suppressors are both derived from an herbal medicine (lei gong teng) that has been used for decades to treat immune diseases. The 6 activators all belonged to a group of chemicals known as flavonoids, widely distributed among dietary fruits and vegetables. CONCLUSION: Several common dietary products that contain certain flavonoids might be environmental risk factors for AS; the Chinese traditional herb lei gong teng might be a potential drug for patients who are HLA-B27-positive. These results provide new research directions for the pathogenesis and therapeutics of AS.

Early diagnosis crucial in ankylosing spondylitis.

Ankylosing spondylitis (AS) is an inflammatory autoimmune disorder that predominantly affects the spine. If untreated it may cause significant morbidity. Early diagnosis is particularly important as newer therapies are able to contain this condition and even induce remission. AS affects about 0.2-0.5% of the population. It is at least twice as common in men and most often manifests in the third to fifth decades. It is estimated that up to 5% of patients with chronic lower back pain in primary care have inflammatory disease. Although only 1% of patients with HLA-B27 develop AS, 90-95% of patients with AS are positive for HLA-B27. Immune dysfunction is the hallmark of this condition and it may be triggered by infection. The primary site of inflammation in AS is the entheses, the sites of insertion of tendons and ligaments into bone. If the inflammation remains untreated, there is resultant fibrosis and ultimately ossification at the entheseal sites. AS should be suspected in patients who report back pain and stiffness with rest, especially in the morning, which improves with exercise. Although the condition affects both the sacroiliac joints, a proportion of patients report pain radiating into the buttocks which may be unilateral or alternate, particularly in the early stages. In addition to the spine, large joint synovitis may develop as well as features of entheseal involvement. New classification criteria take into account early sacroiliitis evident on MRI scan and allow a diagnosis to be made far earlier than was previously possible. A proportion of patients respond well to NSAIDs coupled with a structured physiotherapy and exercise programme. However, about half these patients need escalation to biologic therapy. Patients with a suspected diagnosis should be referred to secondary care in order to confirm the diagnosis and commence treatment.

Supplemental calcium attenuates the colitis-related increase in diarrhea, intestinal permeability, and extracellular matrix breakdown in HLA-B27 transgenic rats.

We have shown in several controlled rat and human infection studies that dietary calcium improves intestinal resistance and strengthens the mucosal barrier. Reinforcement of gut barrier function may alleviate inflammatory bowel disease (IBD). Therefore, we investigated the effect of supplemental calcium on spontaneous colitis development in an experimental rat model of IBD. HLA-B27 transgenic rats were fed a purified high-fat diet containing either a low or high calcium concentration (30 and 120 mmol CaHPO4/kg diet, respectively) for almost 7 wk. Inert chromium EDTA (CrEDTA) was added to the diets to quantify intestinal permeability by measuring urinary CrEDTA excretion. Relative fecal wet weight was determined to quantify diarrhea. Colonic inflammation was determined histologically and by measuring mucosal interleukin (IL)-1beta. In addition, colonic mucosal gene expression of individual rats was analyzed using whole-genome microarrays. The calcium diet significantly inhibited the increase in intestinal permeability and diarrhea with time in HLA-B27 rats developing colitis compared with the control transgenic rats. Mucosal IL-1beta levels were lower in calcium-fed rats and histological colitis scores tended to be lower (P = 0.08). Supplemental calcium prevented the colitis-induced increase in the expression of extracellular matrix remodeling genes (e.g. matrix metalloproteinases, procollagens, and fibronectin), which was confirmed by quantitative real-time PCR and gelatin zymography. In conclusion, dietary calcium ameliorates several important aspects of colitis severity in HLA-B27 transgenic rats. Reduction of mucosal irritation by luminal components might be part of the mechanism. These results show promise for supplemental calcium as effective adjunct therapy for IBD.

A monoclonal antibody against kininogen reduces inflammation in the HLA-B27 transgenic rat.

The human leukocyte antigen B27 (HLA-B27) transgenic rat is a model of human inflammatory bowel disease, rheumatoid arthritis and psoriasis. Studies of chronic inflammation in other rat models have demonstrated activation of the kallikrein-kinin system as well as modulation by a plasma kallikrein inhibitor initiated before the onset of clinicopathologic changes or a deficiency in high-molecular-mass kininogen. Here we study the effects of monoclonal antibody C11C1, an antibody against high-molecular-mass kininogen that inhibits the binding of high-molecular-mass kininogen to leukocytes and endothelial cells in the HLA-B27 rat, which was administered after the onset of the inflammatory changes. Thrice-weekly intraperitoneal injections of monoclonal antibody C11C1 or isotype IgG1 were given to male 23-week-old rats for 16 days. Stool character as a measure of intestinal inflammation, and the rear limbs for clinical signs of arthritis (tarsal joint swelling and erythema) were scored daily. The animals were killed and the histology sections were assigned a numerical score for colonic inflammation, synovitis, and cartilage damage. Administration of monoclonal C11C1 rapidly decreased the clinical scores of pre-existing inflammatory bowel disease (P < 0.005) and arthritis (P < 0.001). Histological analyses confirmed significant reductions in colonic lesions (P = 0.004) and synovitis (P = 0.009). Decreased concentrations of plasma prekallikrein and high-molecular-mass kininogen were found, providing evidence of activation of the kallikrein-kinin system. The levels of these biomarkers were reversed by monoclonal antibody C11C1, which may have therapeutic potential in human inflammatory bowel disease and arthritis.

Hepatocyte growth factor treatment ameliorates diarrhea and bowel inflammation in a rat model of inflammatory bowel disease.

BACKGROUND/PURPOSE: Transfection of the HLA-B27 gene into normal Fischer rats induces phenotypic changes similar to inflammatory bowel disease (IBD). This study investigated the benefits of 2 doses of hepatocyte growth factor (HGF) on the manifestations of IBD in this rat model. METHODS: Fischer rats and HLA-B27 rats were divided into 4 groups: Fischer rats treated with saline, HLA-B27 rats treated with saline, HGF at 150 microg/kg/d, and HGF at 300 microg/kg/d. HGF or saline was infused for 14 days via an osmotic pump attached to a catheter in the internal jugular vein. After treatment, rats were evaluated for diarrhea and reduction in gross and microscopic bowel inflammation. Statistics were determined using analysis of variance (ANOVA). A P value < or =.05 was considered significant. RESULTS: Administration of HGF at 150 microg/kg/d decreased diarrhea by 40%, gross inflammation by 41%, and microscopic inflammation by 72% (P < or =.05). At 300 microg/kg/d HGF decreased diarrhea by 46%, gross inflammation by 45%, and microscopic inflammation by 54% (P < or =.05). CONCLUSIONS: HGF administration reduces the clinical manifestations of IBD in this rat model. Similar effects were seen at both doses of HGF administration, implying that there is a plateau above which further increases in HGF levels provides no added benefit. HGF administration may be clinically useful in the management of IBD.

Intestinal anti-inflammatory activity of dietary fiber (Plantago ovata seeds) in HLA-B27 transgenic rats.

BACKGROUND & AIMS: Dietary fiber has been proven to be beneficial in maintaining remission in human ulcerative colitis, an effect related with an increased luminal production of short-chain fatty acids (SCFA). The aim of the present study was to further investigate the mechanisms involved in the intestinal anti-inflammatory effects of dietary fiber in an experimental model of rat colitis. METHODS: HLA-B27 transgenic rats (8-10 weeks old) were fed a fiber-supplemented diet (5% Plantago ovata seeds) for 13 weeks before evaluation of the colonic inflammatory status, both histologically and biochemically. The luminal colonic production of SCFA was quantified. In vitro studies were also performed to test the interaction between two SCFA (butyrate and propionate) as inhibitors of cytokine production in THP-1 cells. RESULTS: Dietary fiber supplementation ameliorated the development of colonic inflammation in transgenic rats as evidenced by an improvement of intestinal cytoarchitecture. This effect was associated with a decrease in some of the pro-inflammatory mediators involved in the inflammatory process: nitric oxide, leukotriene B(4), tumor necrosis factor alpha (TNFalpha). The intestinal contents from fiber-treated colitic rats showed a significant higher production of SCFA, butyrate and propionate, than non-treated colitic animals. In vitro studies revealed a synergistic inhibitory effect of butyrate and propionate on TNFalpha production. CONCLUSIONS: Dietary fiber supplementation ameliorated colonic damage in HLA-B27 transgenic rats. This effects was associated with an increased production of SCFA, which can act synergistically in inhibiting the production of pro-inflammatory mediators.

The clinical experience of antisense therapy to ICAM-1 in Crohn's disease.

ISIS-2302 is a 6781.24 amu molecular weight antisense molecule. Its sequence is 5'-GCCCAAGCTGGCATCCGTCA-3'. This 20 base phosphorothioate hybridizes to a sequence in the 3' untranslated region of human ICAM-1 mRNA. This substrate is cleaved by RNase H, resulting in specific message and protein reduction 11,21.

Experimental autoimmune uveitis in HLA-B27 transgenic mice.

The major histocompatibility complex (MHC) gene, HLA-B27 is strongly associated with auto-immune uveitis and spondyloarthropathies in humans. Experimental mouse models of autoimmune uveitis involve systemic immunization with the retinal autoantigen interphotoreceptor retinoid binding protein (IRBP). To assess possible roles of HLA-B27 in autoimmune uveitis, as well as to investigate a possible new animal model of human uveitis, inbred strains of C57BL/6 and C57BL/6 possessing the human HLA-B27 or HLA-A2 transgene were immunized with IRBP emulsified in complete Freund's adjuvant (CFA). Dilated eye examinations were performed to assess the timing and clinical course of any ensuing uveitis. Mice were sacrificed 3 to 4 weeks postinjection and the eyes submitted for histopathologic analysis. CFA alone did not produce any clinical uveitis. Fifty percent of eyes from the background C57BL/6 strain developed uveitis as early as 10 days postinjection. Of the eyes demonstrating uveitis, an average clinical score of 2.5 was present. Pathologically, a moderate scleritis and anterior uveitis was present. Fifty percent of A2 transgenic eyes developed uveitis as early as 14 days postinjection with an average clinical score of 2.0. Pathologically, a mild vitritis was present. Uveitis developed in only 20% of B27 transgenic mice and reached a peak on day 28. The average EAU score in diseased animals was 4.5. A dense retinitis and panuveitis was associated with severe vitritis. We conclude that the presence of the B27 gene is associated with a decreased incidence and slower rate of onset of EAU following immunization with IRBP; however, EAU may be more severe in the HLA-B27 expressing animals who do develop disease.

Role of endogenous enteric organisms in the reactivation of arthritis.

Reactive arthritis is an acute form of arthritis apparently caused by a combination of bacterial infection and genetic influences. Recent experiments using an animal model suggest that certain bacterial cell wall polymers originating from endogenous enteric bacteria may be responsible for the condition.