Immunological biomarkers in patients with radiographic axial spondyloarthritis, an exploratory longitudinal Swedish study

Objectives There is a need for more specific biomarkers to diagnose and predict disease course in patients with axial spondyloarthritis (axSpA). This study aimed to study immunological plasma biomarkers, at different time-points in radiographic (r)-axSpA patients overall and stratified by sex and compare these biomarker pattern in r-axSpA patients concerning disease phenotypes and disease activity. Methods Plasma samples were analysed from r-axSpA patients at and prior (Pre-Backbone) inclusion in the Backbone study. Interferon gamma, interleukin-10, -17A, -17F, -22, -23, -6, MCP-1, TNF-α, VEGF-A, MIF, IgA anti-CD74, zonulin, ESR, hsCRP, white blood cell count, and blood lipids were measured. Results Biomarker pattern discriminated significantly between r-axSpA patients in Backbone and Pre-Backbone compared with controls. When stratifying by sex, it was possible to discriminate between male and female r-axSpA patients in Backbone vs controls and between male r-axSpA patients in pre-Backbone and controls. In Backbone, markers with high discriminative capacity were MIF, IgA anti-CD74, and MCP-1. In Pre-Backbone, IL-6, TNF-α, MIF, triglycerides, cholesterol, IL-10, and zonulin displayed high discriminative capacity. Conclusion Based on their temporal pattern and mutual relationship, we suggest studying MIF, IgA anti-CD74, and MCP-1 in depth, at more time points, to further elucidate disease-driving mechanisms in this complex disease.

Increased carotid intima-media thickness in patients with radiographic axial spondyloarthritis compared to controls and associations with markers of inflammation

OBJECTIVE

There is an increased risk for cardiovascular disease (CVD) in patients with radiographic axial spondyloarthritis (r-axSpA). In this cross-sectional study, we aimed to, overall and stratified by sex, (i) compare ultrasound derived carotid intima media thickness (cIMT), between patients and controls, and (ii) investigate associations between cIMT, clinical disease activity and inflammation-related laboratory markers in patients with r-axSpA.

METHOD

In total, 155 patients diagnosed with r-axSpA using the modified New York criteria and 400 controls were included. Bilateral carotid ultrasound, laboratory testing, and questionaries were acquired. Disease-specific assessments were carried out for patients. Linear regression analysis was used to assess associations.

RESULTS

Linear regression analyses showed that patients with r-axSpA had increased mean cIMT compared to controls (mean ± SD, 0.8 ± 0.1 mm vs 0.7± 0.1 mm, respectively, unstandardized β (95% CI) -0.076 (-0.10, -0.052), P < 0.001) adjusted for smoking status and age. Linear regression analyses for patients with r-axSpA showed that only males presented significant associations between cIMT and inflammation-related laboratory markers, white blood cell (WBC) count (mean ± SD, 6.8 ± 1.6 109/L) and monocytes (0.6 ± 0.2 109/L); WBC count (unstandardized β (95% CI) 0.019 (0.0065, 0.031), P = 0.003, R2 = 0.57) and monocytes (0.13 (0.0047, 0.26), P = 0.041, R2 = 0.55), adjusted for age, smoking status, body mass index, hypertension, dyslipidemia, diabetes mellitus, ASDAS-CRP, and treatment with DMARDs and glucocorticoids. No significant association was found between cIMT and clinical disease activity assessed by ASDAS-CRP.

CONCLUSION

Patients with r-axSpA had significantly increased cIMT compared to controls. In male patients, higher WBC and monocyte count were associated with an increase in cIMT suggesting the role of inflammation in the development of atherosclerosis. Key Points •Carotid intima-media thickness was increased in patients with radiographic axial spondyloarthritis compared to controls. •White blood cell and monocyte counts were associated with carotid intima-media thickness in male patients with radiographic axial spondyloarthritis.

Protein profiling in pre-symptomatic individuals separates MPO-ANCA and PR3-ANCA vasculitides

OBJECTIVE

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a chronic relapsing condition with unknown etiology. To gain insight into molecular processes underlying the disease, we examined biomarkers in blood samples collected prior to symptom onset. Methods The National Patient Register and Cause of Death register were searched for AAV-ICD-codes and linked to the registers from five biobanks. Eighty-five AAV-cases with samples predating symptom onset of AAV were identified. For each case two matched controls were included. Proteinase 3 (PR3)-ANCA and myeloperoxidase (MPO)-ANCA were analyzed using enzyme-linked immunosorbent assays. Using Olink Inflammation panel, we included 73 of 92 proteins after quality control. Data was replicated in a second cohort of 48 pre-symptomatic cases and 96 controls.

RESULTS

Of the 20 proteins with the lowest p-value in the original cohort seven were replicated in the second cohort and in a meta-analysis five were significant between the groups. Eleven different pathways were identified in network enrichment analyses and were significant in both cohorts. Stratification of samples obtained ≤5 years before onset showed significant levels of CCL23, VEGF-A, HGF and borderline in the replication cohort besides IL-6. In pre-AAV cases, six proteins were associated with MPO-ANCA+, and seven proteins with PR3-ANCA+.

CONCLUSION

To our knowledge, this is the first study to identify protein markers preceding symptom onset in AAV. These findings set the stage for further research into underlying cellular and molecular mechanisms in AAV pathogenesis and the diversification into the PR3-ANCA and MPO-ANCA sub-phenotypes. This article is protected by copyright. All rights reserved.

HSC70 is a novel binding partner involved in the capture of immunoglobulins on B cells in the NOD mouse

B cells have been shown to be essential for Type 1 diabetes development in the non-obese diabetic mouse, where their contribution as antigen presenting cells has been emphasised. Other important functions for B cells include surface capture of immunoglobulins and transportation of immune complexes, with subsequent endocytosis, antigen processing and antigen presentation. We have previously demonstrated that NOD B cells capture IgM and IgG immune complexes through an unknown surface molecule. In this study, we revealed the presumptive immunoglobulin-binding molecule to be HSC70. Moreover, we detected increased levels of HSC70 on NOD B cells. HSC70 has been shown to play a role in antigen processing and presentation as well as being important in several autoimmune diseases, including rheumatoid arthritis and systemic lupus erythematosus. Due to its protein stabilising properties, increased HSC70 could contribute to enhanced self-antigen collection and presentation and thereby contribute to the development of Type 1 diabetes.

POS0245 PROTEIN PROFILING IN PRE-SYMPTOMATIC ANCA-ASSOCIATED VASCULITIS INDIVIDUALS

Background

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a rare chronic relapsing condition, with unknown etiology.

Objectives

This study was undertaken to gain insight to the molecular processes and to find potential biomarkers in blood samples collected prior to the onset of symptoms of AAV.

Methods

The National Patient Register and Cause of Death register were searched for AAV-ICD codes and linked to the registers of five biobanks. Eighty-five AAV cases were identified (34 males, 51 females) with samples >1month <10years from AAV symptom onset. For each case two controls matched for sex, age, and sampling date were included. Samples were analyzed using ELISAs for PR3- or MPO-ANCA specificities. Ninety-two protein markers were analyzed using Olink Inflammation panel, (OLINK, Uppsala, Sweden) with 73 eligible after quality control.

Results

Eight protein markers were significantly altered between pre-AAV and controls, with higher levels of CCL23, CXCL5 (p< 0.01-0.05) and lower levels of Flt3L, STAMBP, ADA, TNFB, CX3CL1 and IL-15RA (p< 0.01-0.05) in the pre-AAV individuals. Nine protein markers were found significantly associated with time to symptom onset; CXCL9, CD244, VEGFA, CXCL1, TNFSF9, OPG, CSF-1, IFN-gamma and CD40 (p< 0.01-0.05). In pre-AAV individuals, six proteins were associated with MPO-ANCA-positivity compared with the MPO-ANCA-negative pre-AAV individuals which showed no overlap with the seven proteins related to PR3-ANCA-positivity.

Conclusion

To our knowledge our study is the first to analyze for and identify protein markers before symptom onset in AAV. This allowed for further studies of underlying cellular and molecular mechanisms in AAV pathogenesis as well as the diversification into PR3-ANCA and MPO-ANCA subphenotypes.

Disclosure of Interests

Mikael Brink: None declared, Ewa Berglin: None declared, Aladdin J Mohammad Speakers bureau: Roche, Gsk, AMGEN; Vifor, Lilly, Consultant of: Roche & AMGEN, Andrey Alexeyenko: None declared, Kristina Lejon: None declared, Solbritt Rantapää Dahlqvist: None declared

Increased proportions of inflammatory T cells and their correlations with cytokines and clinical parameters in patients with ankylosing spondylitis from northern Sweden

Ankylosing spondylitis (AS) is an autoimmune disease affecting parts of the skeletal structure in particular. Previously increased levels of the inflammatory cell types Th17, Th22, Tc17 and Tc22 cells have been shown to be associated with AS. Here, we analysed the levels of inflammatory T cell subsets, related cytokines and clinical characteristics of AS patients vs controls from northern Sweden. Peripheral blood mononuclear cells (PBMCs) obtained from 50 AS patients and 50 matched controls were short term stimulated with PMA/Ionomycin, stained and analysed by flow cytometry. Plasma levels of Interleukin (IL)‐17, IL‐22, IL‐10 as well as clinically relevant markers were determined. Compared to male controls, male AS patients showed 1.5‐ to 2‐fold increases of Th17 (P = .013), Th22 (P = .003) and Tc22 (P = .024) among CD45⁺CD3⁺ lymphocytes. Plasma IL‐22 levels correlated with the Tc17 proportion in male patients (R_s = 0.499, P = .003) and plasma IL‐10 levels were inversely correlated with Tc17 among all patients (R_s = −0.276, P = .05). Male patients with syndesmophytes showed significantly higher Th17 proportions (P = .038). In female AS patients, Tc22 was negatively correlated with C‐reactive protein (high sensitivity) (hsCRP) (R_s = −0.573, P = .016). We confirmed increased proportions of inflammatory T cells and correlations with relevant cytokines from male AS patients. The correlation between Th17 and syndesmophytes supports a role of Th17 in the pathogenic process.

Anti-CD74 IgA autoantibodies in radiographic axial spondyloarthritis: a longitudinal Swedish study

Objectives

Antibodies against anti-CD74 are related to axial spondyloarthritis (axSpA). The objectives were (i) to study IgA anti-CD74 in radiographic (r)-axSpA patients in the Backbone cohort and to calculate the sensitivity and specificity of anti-CD74, (ii) to study the fluctuation of IgA anti-CD74 levels in prospectively collected samples, and (iii) to explore the relation between IgA anti-CD74 and radiographic spinal changes.

Methods

IgA anti-CD74 was analysed by ELISA in 155 patients with r-axSpA and age- and sex-matched controls. BASDAI, ASDAS, BASFI and BASMI were assessed and spinal radiographs were scored for r-axSpA-related changes with mSASSS. Previously donated samples, before inclusion in the Backbone study, were identified in the Medical Biobank of Northern Sweden.

Results

A total of 155 patients comprising 69% men and 31% women, age [mean (s.d.)] 55.5 (11.4) years and 152 (98.1%) HLA-B27 positive, were included. The plasma level of IgA anti-CD74 was significantly higher in the patients [median (interquartile range), 12.9 (7.9–17.9) U/ml] compared with controls [10.9 (7.2–14.6) U/ml, P = 0.003]. IgA anti-CD74 was above the cut-off level of 20 U/ml in 36/155 (23.2%) patients and in 15/151 (9.9%) controls (P = 0.002). Multivariable logistic regression analyses revealed ≥1 syndesmophyte associated with IgA anti-CD74 (odds ratio 5.64; 95% CI: 1.02, 35.58; P = 0.048) adjusted for hsCRP, smoking, BMI, sex and age. No distinct pattern of IgA anti-CD74 over time was revealed.

Conclusion

Plasma levels of IgA anti-CD74 were increased in r-axSpA and independently associated with radiographic spinal changes, which suggests that IgA anti-CD74 could play a role in the pathogenies of r-axSpA.

OP0024 DECREASED LEVELS OF T FOLLICULAR HELPER (CD4+CXCR5+) CELLS AND CD27+CD38+ AND CD27+CD38- B CELLS IN ANKYLOSING SPONDYLITIS PATIENTS CORRELATE WITH MARKER OF INFLAMMATION

Background:

The role of different lymphocyte subsets in ankylosing spondylitis (AS) is still to be elucidated. It has previously been reported contradictory data concerning the levels of T Follicular Helper (TFH) cells and differentiated B cells in peripheral blood of AS patients. In addition, the connection to disease related parameters is still to be fully revealed.

Objectives:

The purpose of this study was to investigate the level of CD4+TFH cells and CD27+CD38+/CD38- B cells in patients with AS from northern Sweden and to compare the levels with age and sex-matched controls. We also studied associations between these cell subsets and disease related factors.

Methods:

Peripheral blood mononuclear cells (PBMSc) from a cohort of 50 patients with AS from Region Västerbotten (mean age 52±9.1 years, 33 (66 %) men, 50 (100 %) HLAB27 positive) and 50 pair wise matched blood donor controls (mean age 54±8.8 years, 33 (66 %) men) were stained with a combination of antibodies allowing for the detection of CD27, CD38, CD19, CD3, CD4 and CXCR5 markers and analyzed by flow cytometry. In addition, the patient with AS were examined with spinal x-ray for radiographic alterations assessed with mSASSS. CRP and ESR were measured and physical function and disease activity were registered with BASMI and BASFI respectively ASDAS-CRP and BASDAI.

Results:

When comparing AS patients and controls pair wise, we observed on average a 50% reduction of TFH (CD3+CD4+CXCR5+) cells among CD45+ lymphocytes in PBMCs from patients (p=0,000008). Furthermore, a 20-30% reduction among memory/plasma cells (CD19+CD27+CD38+ and CD19+CD27+CD38-) among CD45+ lymphocytes in PBMCs from patients (p=0,002 and p=0,007 respectively). For female patients a correlation between TFH and ESR (Rs=-0,551 p=0,022) was observed. Moreover, negative correlations between the two B cell subsets (CD19+CD27+CD38+ and CD19+CD27+CD38-) and ESR were observed for female patients (Rs =–0,476 p=0,053 and Rs =–0,522 p=0,032 respectively).

Conclusion:

TFH cells was reduced in AS patients and this reduction correlated with a reduction in differentiated (CD27+CD38+ and CD27+CD38-) B cells. In addition, the inflammation marker ESR was negatively correlated with TFH as well as with the differentiated B cell subsets in female patients. Our observations indicates a role of the humoral immune response in AS.

Disclosure of Interests:

None declared

THU0296 PROTEIN PROFILING IN INDIVIDUALS BEFORE ONSET OF ANCA-ASSOCIATED VASCULITIS

Background:

Etiology and pathogenesis of ANCA-associated vasculitis (AAV) is multifactorial and understanding of the processes leading from a healthy immune system to autoimmunity and on to debut of symptoms in AAV is rudimentary.

Objectives:

To identify inflammatory proteins related to the early processes preceding AAV development, and potential novel biomarkers, using large-scale protein analyses

Methods:

The Swedish National Patient Register of in-patient carevand the Swedish Cause of Death Register with discharge diagnosis from ICD-9 and-10 for AAV were co-analysed with the registers of 4 different blood biobanks to identify AAV individuals with available samples predating onset of symptom. Of the pre-AAV cases 86 (36 male, 50 female; mean age (SD); 51.9 (16.9) years) were identified with at least one plasma or serum sample (28 plasma, and 100 serum) pre-dating symptom onset (mean (SD); -4.3 (3.1) years), and 14 had 2-3 samples. Serum and plasma control samples matched for sex, age and sampling date were identified (n=198; 82 male, 116 female; mean age (SD); 51.9±15.9 years). The samples were analysed for levels of 92 proteins using proximity extension assay (OLINK inflammation panel, SciLifeLab, Uppsala, Sweden). Data were analysed using routine statistical methods, random forest and Partial Least square-discriminant analysis (PLS-DA).

Results:

As previously described for the assay significant difference between plasma and serum samples were observed both in pre-AAV individuals and controls. In pre-AAV plasma samples significantly increased concentrations of interleukin (IL)-2, chemokine ligand (CCL)-4, fibroblast growth factor (FGF)21, IL-4 and CCL20 were found closer to symptom onset, (<5 years) than later (> 5 years) and compared with controls. In serum tumor necrosis factor receptor superfamily member (TNFRSF)9, CXCL9, osteoprotegerin and vascular endothelial growth factor-A were significantly increased <5 years before onset vs. later (>5 years) and compared with controls. PLS-DA score scattered plot separated the pre-AAV individuals from healthy controls (R2=0.26), with significantly increased levels of CCL23, CXCL5, and matrix metalloproteinases-1 (MMP-1),transforming growth factor-ß, orosomucoid, en-rage (S100A12) and IL-7 and decreased FGF-19 level in serum. Binary logistic regression analyses comparing tertiles for these proteins confirmed significantly increased odds ratios for disease development of CCL23, CXCL5 and MMP-1. The findings were confirmed in random forest analysis where these factors were among the 20 most discriminatory factors between pre-symptomatic AAV and controls.

Conclusion:

In serum samples collected years before symptom onset of AAV, proteins involved in immune system activation were increased, suggesting that the inflammatory process is initiated long before clinical manifestations of the disease appear. These findings propose the elevated proteins as novel biomarkers for disease progression.

References:

[1]Watts et al. Ann Rheum Dis 2007;66:222-22

Acknowledgments:

Vasculitis Foundation, USA

Disclosure of Interests:

Ewa Berglin: None declared, Anders Esberg: None declared, Johanna Dahlqvist: None declared, Johanna Sjöwall: None declared, Anders Lundquist: None declared, Kristina Lejon: None declared, Ingegerd Johansson: None declared, Aladdin J Mohammad Speakers bureau: lecture fees from Roche and Elli Lilly Sweden, PI (GiACTA study), Solbritt Rantapää Dahlqvist: None declared

Protein profiling and network enrichment analysis in individuals before and after the onset of rheumatoid arthritis

Background

Antibodies and upregulated cytokines and chemokines predate the onset of rheumatoid arthritis (RA) symptoms. We aimed to identify the pathways related to the early processes leading to RA development, as well as potential novel biomarkers, using multiple protein analyses.

Methods

A case-control study was conducted within the Biobank of northern Sweden. The plasma samples from 118 pre-symptomatic individuals (207 samples; median predating time 4.1 years), 79 early RA patients, and 74 matched controls were analyzed. The levels of 122 unique proteins with an acknowledged relationship to autoimmunity were analyzed using 153 antibodies and a bead-based multiplex system (FlexMap3D; Luminex Corp.). The data were analyzed using multifactorial linear regression model, random forest, and network enrichment analysis (NEA) based on the 10 most significantly differentially expressed proteins for each two-by-two group comparison, using the MSigDB collection of hallmarks.

Results

There was a high agreement between the different statistical methods to identify the most significant proteins. The adipogenesis and interferon alpha response hallmarks differentiated pre-symptomatic individuals from controls. These two hallmarks included proteins involved in innate immunity. Between pre-symptomatic individuals and RA patients, three hallmarks were identified as follows: apical junction, epithelial mesenchymal transition, and TGF-β signaling, including proteins suggestive of cell interaction, remodulation, and fibrosis. The adipogenesis and heme metabolism hallmarks differentiated RA patients from controls.

Conclusions

We confirm the importance of interferon alpha signaling and lipids in the early phases of RA development. Network enrichment analysis provides a tool for a deeper understanding of molecules involved at different phases of the disease progression.

Innate lymphoid cells are present in gingivitis and periodontitis

BACKGROUND

Innate lymphoid cells (ILCs) are the most recently identified leukocytes of the immune system and these cells are increasingly acknowledged to play important roles in host defence and tissue repair. ILCs are also contributors of inflammatory diseases such as asthma and colitis. We analyzed the presence and relative proportions of the different ILC subsets (ILC1, ILC2 and ILC3) in gingivitis and periodontitis. Further, we investigated if ILCs express receptor activator of nuclear factor kappa-B ligand (RANKL), a cytokine crucial for osteoclast differentiation and bone resorption.

METHODS

We collected gingivitis and periodontitis soft tissue and characterized ILC subsets including RANKL expression in single-cell suspensions using flow cytometry.

RESULTS

ILCs were detected both in gingivitis and periodontitis. The majority of ILCs, in both conditions, were ILC1s. Furthermore, RANKL expression was detected on a fraction of the ILC1s.

CONCLUSIONS

Our discovery of the presence of ILCs both in gingivitis and periodontitis and concomitant expression of RANKL on a fraction of the ILC1 population suggest that these cells may be of importance in periodontal disease. In addition, our findings provide a new insight into the field of oral immunology.

Contribution of both B-cell intrinsic alterations as well as non-hematopoietic-derived factors in the enhanced immune response of the NOD mouse

The underlying cellular and molecular mechanism for the development of Type 1 diabetes is still to be fully revealed. We have previously demonstrated that the NOD mouse, a model for Type 1 diabetes, display a prolonged and enhanced immune response to both self and non-self-antigens. The molecular explanation for this defect however, has not been determined. In this study we immunized NOD and C57BL/6 (B6) with the conventional antigen i.e. hen egg lysozyme (HEL) and analyzed B cell activation, germinal center reaction and antibody clearance. Corroborating our previous observations NOD mice responded robustly to a single immunization of HEL. Immunofluorescence analysis of the spleen revealed an increased number of germinal centers in unimmunized NOD compared to B6. However, post immunization germinal center numbers were similar in NOD and B6. NOD mice showed lower response to BCR stimulation with anti-IgM, in particular at lower concentrations of anti-IgM. Antibody clearance in vivo did not differ between the strains. To determine the cell type that is responsible for the prolonged and enhance immune response, we reconstituted NOD-RAGs with cells from primed donors in different combinations. NOD B cells were required to reproduce the phenotype; however the non-lymphoid compartment of NOD origin also played a role. Based on our results we propose that preexisting GCs in the NOD promote the robust response and alteration in the BCR signaling could promote survival of stimulated cells. Overall, this mechanism could in turn also contribute to the activation and maintenance of autoreactive B cells in the NOD mouse.

Elevated systemic glutamic acid level in the non-obese diabetic mouse is Idd linked and induces beta cell apoptosis

Although type 1 diabetes (T1D) is a T-cell-mediated disease in the effector stage, the mechanism behind the initial beta cell assault is less understood. Metabolomic differences, including elevated levels of glutamic acid, have been observed in patients with T1D before disease onset, as well as in pre-diabetic non-obese diabetic (NOD) mice. Increased levels of glutamic acid damage both neurons and beta cells, implying that this could contribute to the initial events of T1D pathogenesis. We investigated the underlying genetic factors and consequences of the increased levels of glutamic acid in NOD mice. Serum glutamic acid levels from a (NOD×B6)F₂ cohort (n = 182) were measured. By genome-wide and Idd region targeted microsatellite mapping, genetic association was detected for six regions including Idd2, Idd4 and Idd22. In silico analysis of potential enzymes and transporters located in and around the mapped regions that are involved in glutamic acid metabolism consisted of alanine aminotransferase, glutamic-oxaloacetic transaminase, aldehyde dehydrogenase 18 family, alutamyl-prolyl-tRNA synthetase, glutamic acid transporters GLAST and EAAC1. Increased EAAC1 protein expression was observed in lysates from livers of NOD mice compared with B6 mice. Functional consequence of the elevated glutamic acid level in NOD mice was tested by culturing NOD. Rag2^-/- Langerhans' islets with glutamic acid. Induction of apoptosis of the islets was detected upon glutamic acid challenge using TUNEL assay. Our results support the notion that a dysregulated metabolome could contribute to the initiation of T1D. We suggest that targeting of the increased glutamic acid in pre-diabetic patients could be used as a potential therapy.

Increased expression of TACI on NOD B cells results in germinal centre reaction anomalies, enhanced plasma cell differentiation and immunoglobulin production

B cells have an important pathogenic role in the development of type 1 diabetes in the non-obese diabetic (NOD) mouse. We have previously reported that NOD mice display an increased percentage of TACI^high -expressing B cells compared with C57BL/6 mice and this trait is linked to chromosomes 1 and 8. In this paper the genetic association of the transmembrane activator, calcium modulator and cyclophilin ligand interactor (TACI) trait was confirmed using double congenic NOD.B6C1/Idd22 mice. TACI ligation by a proliferation-inducing ligand (APRIL) has been shown to influence plasma cell differentiation, immunoglobulin production and isotype switch. Hence, the functional consequence of the up-regulation of TACI on NOD B cells was analysed both in vitro and in vivo. NOD B cells stimulated with APRIL showed an enhanced plasma cell differentiation and class switch to IgG and IgA compared with B cells from C57BL/6 mice. Moreover, flow cytometry analyses revealed that germinal centre B cells in NOD failed to down-regulate TACI. Availability of the TACI ligand B-cell activating factor (BAFF) has been shown to be a limiting factor in the germinal centre reaction. In line with this, upon immunization with 4-hydroxy-3-nitrophenylacetyl hapten-conjugated hen egg lysozyme, NOD mice produced higher titres of low-affinity antibodies compared with C57BL/6 mice. This observation was supported by the detection of increased levels of BAFF in NOD germinal centres after immunization compared with C57BL/6 by immunofluorescence. Our results support the hypothesis that increased TACI expression on NOD B cells contributes to the pathogenesis of type 1 diabetes in the NOD mouse.

Cytotoxic immune responses in the lungs correlate to disease severity in patients with hantavirus infection

Hantavirus infections may cause severe and sometime life-threatening lung failure. The pathogenesis is not fully known and there is an urgent need for effective treatment. We aimed to investigate the association between pulmonary viral load and immune responses, and their relation to disease severity. Bronchoscopy with sampling of bronchoalveolar lavage (BAL) fluid was performed in 17 patients with acute Puumala hantavirus infection and 16 healthy volunteers acting as controls. Lymphocyte subsets, granzyme concentrations, and viral load were determined by flow cytometry, enzyme-linked immunosorbent assay (ELISA), and quantitative reverse transcription polymerase chain reaction (RT-PCR), respectively. Analyses of BAL fluid revealed significantly higher numbers of activated CD8⁺ T cells and natural killer (NK) cells, as well as higher concentrations of the cytotoxins granzymes A and B in hantavirus-infected patients, compared to controls. In patients, Puumala hantavirus RNA was detected in 88 % of BAL cell samples and correlated inversely to the T cell response. The magnitude of the pulmonary cytotoxic lymphocyte response correlated to the severity of disease and systemic organ dysfunction, in terms of need for supplemental oxygen treatment, hypotension, and laboratory data indicating renal failure, cardiac dysfunction, vascular leakage, and cell damage. Regulatory T cell numbers were significantly lower in patients compared to controls, and may reflect inadequate immune regulation during hantavirus infection. Hantavirus infection elicits a pronounced cytotoxic lymphocyte response in the lungs. The magnitude of the immune response was associated with disease severity. These results give insights into the pathogenesis and possibilities for new treatments.

Non-Hematopoietic and Hematopoietic SIRPα Signaling Differently Regulates Murine B Cell Maturation in Bone Marrow and Spleen

B lymphocyte development occurs in the bone marrow, while final differentiation and maturation can occur in both the bone marrow and the spleen. Here we provide evidence that signal regulatory protein α (SIRPα), an Ig-superfamily ITIM-receptor expressed by myeloid but not by lymphoid cells, is involved in regulating B cell maturation. Lack of SIRPα signaling in adult SIRPα-mutant mice resulted in a reduced maturation of B cells in the bone marrow, evident by reduced numbers of semi-mature IgD⁺IgM^hi follicular type-II (F-II) and mature IgD⁺IgM^lo follicular type-I (F-I) B cells, as well as reduced blood B cell numbers. In addition, lack of SIRPα signaling also impaired follicular B cell maturation in the spleen. Maturing BM or splenic B cells of SIRPα-mutant mice were found to express higher levels of the pro-apoptotic protein BIM and apoptosis was increased among these B cells. Bone marrow reconstitution experiments revealed that the B cell maturation defect in bone marrow and blood was due to lack of SIRPα signaling in non-hematopoietic cells, while hematopoietic SIRPα signaling was important for follicular B cell maturation in the spleen. Adding on to our previous findings of a stromal cell defect in SIRPα-mutant mice was the finding that gene expression of receptor activator of nuclear factor-ĸB ligand (RANKL) was significantly lower in cultured bone marrow stromal cells of SIRPα mutant mice. These data suggest a novel and opposite contribution of SIRPα signaling within non-hematopoietic and hematopoietic cells, respectively, to maintain B cell maturation and to prevent apoptosis in the bone marrow and spleen of adult mice.

Lack of non-hematopoietic SIRPα signaling disturbs the splenic marginal zone architecture resulting in accumulation and displacement of marginal zone B cells

Signal regulatory protein α (SIRPα) is an immunoglobulin super family protein predominantly expressed by myeloid but not lymphoid cells, and its role in lymphocyte homeostasis and function is still to be revealed. We demonstrate that mice bearing a mutant SIRPα lacking the cytoplasmic signaling domain (SIRPα MT) had an increased amount of splenic marginal zone (MZ) B cells compared to wild-type controls. Immunohistochemical analysis revealed an increased localization of MZB cells into B cell follicular areas of the white pulp in SIRPα MT spleens. However, we found no signs of an increased MZB cell activation level in MT mice. The immune response to T-independent antigens in vivo was slightly increased in SIRPα MT mice while sorted MZB from these mice responded normally to LPS in vitro. Bone marrow reconstitution experiments demonstrated that the MZB cell phenotype of SIRPα MT mice was due to lack of SIRPα signaling in non-hematopoietic cells. In contrast, MZ retention of MZ macrophages required hematopoietic SIRPα, while normal distribution of metallophilic macrophages required non-hematopoietic SIRPα signaling. In summary, these data identified SIRPα signaling in non-hematopoietic cells to play an important role in regulating the numbers and positioning MZB cell in the spleen.

Contribution of autoallergy to the pathogenesis in the NOD mice

The immunoglobulin isotype IgE is commonly associated with allergy. However, its involvement in autoimmune disease in general, and Type 1 diabetes (T1D) in particular, is still not completely clarified, nonetheless IgE has been observed in patients with T1D. In this article, we aimed to elucidate the contribution of IgE in the pathogenesis of the disease in a spontaneous model for T1D, i.e. the NOD mouse. We observed increased levels of IgE in splenic, lymph node and peripheral blood B cells in the NOD mice compared to the control C57BL/6 (B6) mice. No correlation was found between the IgE levels on B cells and those in the sera of these mice, indicating a B cell intrinsic property mediating IgE capture in NOD. Functionally, the B cells from NOD were similar to B6 in rescuing the IgE-mediated immune response via the low affinity receptor CD23 in a transgenic adoptive transfer system. However, the involvement of IgE in diabetes development was clearly demonstrated, as treatment with anti-IgE antibodies delayed the incidence of the diabetes in the NOD mice compared to the PBS treated group. Pancreas sections from a 13-week-old NOD revealed the presence of tertiary lymphoid structures with T cells, B cells, germinal centers and IgE suggesting the presence of autoantigen specific IgE. Our study provides an insight to the commonly overlooked immunoglobulin IgE and its potential role in autoimmunity.

Altered metabolic signature in pre-diabetic NOD mice

Altered metabolism proceeding seroconversion in children progressing to Type 1 diabetes has previously been demonstrated. We tested the hypothesis that non-obese diabetic (NOD) mice show a similarly altered metabolic profile compared to C57BL/6 mice. Blood samples from NOD and C57BL/6 female mice was collected at 0, 1, 2, 3, 4, 5, 6, 7, 9, 11, 13 and 15 weeks and the metabolite content was analyzed using GC-MS. Based on the data of 89 identified metabolites OPLS-DA analysis was employed to determine the most discriminative metabolites. In silico analysis of potential involved metabolic enzymes was performed using the dbSNP data base. Already at 0 weeks NOD mice displayed a unique metabolic signature compared to C57BL/6. A shift in the metabolism was observed for both strains the first weeks of life, a pattern that stabilized after 5 weeks of age. Multivariate analysis revealed the most discriminative metabolites, which included inosine and glutamic acid. In silico analysis of the genes in the involved metabolic pathways revealed several SNPs in either regulatory or coding regions, some in previously defined insulin dependent diabetes (Idd) regions. Our result shows that NOD mice display an altered metabolic profile that is partly resembling the previously observation made in children progressing to Type 1 diabetes. The level of glutamic acid was one of the most discriminative metabolites in addition to several metabolites in the TCA cycle and nucleic acid components. The in silico analysis indicated that the genes responsible for this reside within previously defined Idd regions.

Up-regulation of cytokines and chemokines predates the onset of rheumatoid arthritis

OBJECTIVE

To identify whether cytokines, cytokine-related factors, and chemokines are up-regulated prior to the development of rheumatoid arthritis (RA).

METHODS

A nested case-control study was performed in 86 individuals who had donated blood samples before experiencing any symptoms of disease (pre-patients) and 256 matched control subjects (1:3 ratio). In 69 of the pre-patients, blood samples were also obtained at the time of the diagnosis of RA. The plasma levels of 30 cytokines, related factors, and chemokines were measured using a multiplex system.

RESULTS

The levels of several of the cytokines, cytokine receptors, and chemokines were significantly increased in individuals before disease onset compared with the levels in control subjects; i.e., those representing signs of general immune activation (interleukin-1beta [IL-1beta], IL-2, IL-6, IL-1 receptor antagonist, and tumor necrosis factor), activation of Th1 cells (interferon-gamma, IL-12), Th2 cells (IL-4, eotaxin), Treg cells (IL-10), bone marrow-derived factors (IL-7, granulocyte-macrophage colony-stimulating factor, and granulocyte colony-stimulating factor), as well as chemokines (monocyte chemotactic protein 1 and macrophage inflammatory protein 1alpha). The levels were particularly increased in anti-cyclic citrullinated peptide antibody- and rheumatoid factor-positive individuals, and the concentration of most of these increased further after disease onset. The concentration of IL-17 in individuals before disease onset was significantly higher than that in patients after disease onset. Individuals in whom RA subsequently developed were discriminated from control subjects mainly by the presence of Th1 cells, Th2 cells, and Treg cell-related cytokines, while chemokines, stromal cell-derived cytokines, and angiogenic-related markers separated patients after the development of RA from individuals before the onset of RA.

CONCLUSION

Individuals in whom RA later developed had significantly increased levels of several cytokines, cytokine-related factors, and chemokines representing the adaptive immune system (Th1, Th2, and Treg cell-related factors); after disease onset, the involvement and activation of the immune system was more general and widespread.

Idd-linked genetic regulation of TACIhigh expressing B cells in NOD mice

In NOD mice, B cells play a key role in the initiation of type 1 diabetes pathogenesis. We have identified a novel NOD-specific B cell-related trait, i.e. the increased percentage of TACI(high)-expressing splenic B cells, by comparing NOD mice with non-autoimmune C57BL/6 mice. Using athymic NOD mice, we determined that this trait was T cell independent. We mapped the loci contributing to the increased proportion of TACI(high) expressing splenic B cells and found that the control of TACI expression was strongly linked to chromosome 1, in a region which includes the insulin-dependent diabetes (Idd) 5 loci. Moreover, another locus potentially involved was detected in the vicinity of Idd22 on chromosome 8. Interestingly, when analyzing age-dependent contribution to the obtained LOD scores we observed that the linkage to chromosome 8 was explained solely by mice > or =61 days of age, suggesting a temporal genetic regulation of TACI expression. In addition, analysis of genetic interaction between chromosome 1 and chromosome 8 indicated that the two loci acted in an additive fashion. Our findings corroborate the notion that B cell deviations contribute to type 1 diabetes development, and suggest a temporal regulation of TACI(high) expression, possibly influenced by the ongoing autoimmune process.

The NOD allele of the Idd5 locus on chromosome 1 mediates a non-cell-autonomous defect in negative selection of T cells

Recent data have suggested that non-obese diabetic (NOD) mice display a defect in negative thymic selection. Using mixed bone marrow chimeras, we demonstrate that the NOD allele of the diabetes susceptibility region 5 (Idd5) locus on chromosome 1, confers defective negative selection in response to endogenous superantigens (SAg) Mtv8 and Mtv9. We generated mixed bone marrow (BM) chimeras in which the donor cells of NOD and C3H or NOD.Idd5(b10) and C3H coexist and are similarly exposed to the Mtv8 and Mtv9 SAg. Under these conditions, SAg-mediated deletion of Vbeta11+ T cells is less efficient in chimeric mice reconstituted with NOD+C3H BM, compared with chimeras reconstituted with NOD.Idd5(b10)+C3H BM. Interestingly, the observed discrepancy was not T cell autonomous but was found to be mediated by a BM derived cellular subset, and under control of a gene(s) in the Idd5 region.

EDAR mutation in autosomal dominant hypohidrotic ectodermal dysplasia in two Swedish families

Background

Hypohidrotic ectodermal dysplasia (HED) is a genetic disorder characterized by defective development of teeth, hair, nails and eccrine sweat glands. Both autosomal dominant and autosomal recessive forms of HED have previously been linked to mutations in the ectodysplasin 1 anhidrotic receptor (EDAR) protein that plays an important role during embryogenesis.

Methods

The coding DNA sequence of the EDAR gene was analyzed in two large Swedish three-generational families with autosomal dominant HED.

Results

A non-sense C to T mutation in exon 12 was identified in both families. This disease-specific mutation changes an arginine amino acid in position 358 of the EDAR protein into a stop codon (p.Arg358X), thereby truncating the protein. In addition to the causative mutation two polymorphisms, not associated with the HED disorder, were also found in the EDAR gene.

Conclusion

The finding of the p.Arg358X mutation in the Swedish families is the first corroboration of a previously described observation in an American family. Thus, our study strengthens the role of this particular mutation in the aetiology of autosomal dominant HED and confirms the importance of EDAR for the development of HED.

Expression of the NK-1 receptor on islet cells and invading immune cells in the non-obese diabetic mouse

The underlying mechanistic causes of immune cell infiltration in the islets of Langerhans and beta cell failure in the non-obese diabetic (NOD) mouse is still to be completely revealed. Substance P (SP) is a substance known to have pro-inflammatory, endocrine, neuromodulatory and trophic effects, and its preferred receptor, the neurokinin receptor 1 (NK-1 R), is reported to be involved in extravasation of granulocytes and in inflammation and tissue derangement. Therefore, we have investigated the expression of NK-1 R during development of insulitis in the NOD mouse. We show that the magnitude of immunoreactivity scoring NK-1 R expression in the islets was increased in the 12-week-old NOD mouse. Expression of NK-1 R co-localized with expression of glucagon. In line with this expression pattern, we did not detect any effect of SP on glucose-induced insulin release. NK-1 R expression was particularly observed in islet cells in association with the clusters of immune cells. Expression of NK-1 R was also demonstrated in a fraction of the infiltrating B and T lymphocytes, as well as on infiltrating macrophages and dendritic cells. The observations show that the level of NK-1 R expression is increased in 12-week-old NOD mice, being correlated with the occurrence of islet mononuclear infiltration. Our data suggest that SP may act as a chemoattractant, contributing to the pathogenic mononuclear infiltration process in the NOD mouse. On the whole, the observations suggest that SP and the NK-1 R to certain extents are involved in the changes that occur during the development of insulitis in the NOD mouse.

Diabetes protection and restoration of thymocyte apoptosis in NOD Idd6 congenic strains

Type 1 diabetes in the nonobese diabetic (NOD) mouse is a multifactorial and polygenic disease. The NOD-derived genetic factors that contribute to type 1 diabetes are named Idd (insulin-dependent diabetes) loci. To date, the biological functions of the majority of the Idd loci remain unknown. We have previously reported that resistance of NOD immature thymocytes to depletion by dexamethazone (Dxm) maps to the Idd6 locus. Herein, we refine this phenotype using a time-course experiment of apoptosis induction upon Dxm treatment. We confirm that the Idd6 region controls apoptosis resistance in immature thymocytes. Moreover, we establish reciprocal Idd6 congenic NOD and B6 strains to formally demonstrate that the Idd6 congenic region mediates restoration of the apoptosis resistance phenotype. Analysis of the Idd6 congenic strains indicates that a 3-cM chromosomal region located within the distal part of the Idd6 region controls apoptosis resistance in NOD immature thymocytes. Together, these data support the hypothesis that resistance to Dxm-induced apoptosis in NOD immature thymocytes is controlled by a genetic factor within the region that also contributes to type 1 diabetes pathogenesis. We propose that the diabetogenic effect of the Idd6 locus is exerted at the level of the thymic selection process.

The CD8alpha(+) dendritic cell is responsible for inducing peripheral self-tolerance to tissue-associated antigens

We previously described a mechanism for the maintenance of peripheral self-tolerance. This involves the cross-presentation of tissue-associated antigens by a bone marrow-derived cell type that stimulates the proliferation and ultimate deletion of self-reactive CD8 T cells. This process has been referred to as cross-tolerance. Here, we characterize the elusive cell type responsible for inducing cross-tolerance as a CD8alpha(+) dendritic cell (DC). To achieve this aim, transgenic mice were generated expressing yellow fluorescent protein (YFP) linked to CTL epitopes for ovalbumin and glycoprotein B (gB) of herpes simplex virus under the rat insulin promoter (RIP). Although tracking of YFP was inconclusive, the use of a highly sensitive gB-specific hybridoma that produced beta-galactosidase on encounter with antigen, enabled detection of antigen presentation by cells isolated from the pancreatic lymph node. This showed that a CD11c(+)CD8alpha(+) cell was responsible for cross-tolerance, the same DC subset as previously implicated in cross-priming. These data indicate that CD8alpha(+) DCs play a critical role in both tolerance and immunity to cell-associated antigens, providing a potential mechanism by which cytotoxic T lymphocyte can be immunized to viral antigens while maintaining tolerance to self.

The identification and validation of common disease genes: relevance to the drug development process

The understanding of the genetic factors contributing to the development of common diseases has presented a great challenge. Recent accomplishments in the field of genetics have now transformed this vision into a reachable goal. The increased knowledge will have great impact on our fundamental understanding of biological processes, as well as how we diagnose and treat common disease. Many obstacles still remain, and a careful choice of strategy will be critical to achieve these goals. One key point will be the validation of generated candidates in an optimized study set-up.

CD4(+)CD25(+) T cells facilitate the induction of T cell anergy

T cell anergy is characterized by the inability of the T cell to produce IL-2 and proliferate. It is reversible by the addition of exogenous IL-2. A similar state of unresponsiveness is observed when the proliferative response of murine CD4(+)CD25(-) T cells is suppressed in vitro by coactivated CD4(+)CD25(+) T cells. We have developed a suppression system that uses beads coated with anti-CD3 and anti-CD28 Abs as surrogate APCs to study the interaction of CD4(+)CD25(+) and CD4(+)CD25(-) T cells in vitro. CD4(+)CD25(+) T cell-induced suppression, in this model, was not abrogated by blocking the B7-CTLA-4 pathway. When the CD4(+)CD25(-) T cells were separated from the CD4(+)CD25(+) suppressor cells after 24 h of coactivation by the Ab-coated beads, the CD4(+)CD25(-) T cells were unable to proliferate or to produce IL-2 upon restimulation. The induction of this anergic phenotype in the CD4(+)CD25(-) T cells correlated with the up-regulated expression of the gene related to anergy in lymphocytes (GRAIL), a novel anergy-related gene that acts as a negative regulator of IL-2 transcription. This system constitutes a novel mechanism of anergy induction in the presence of costimulation.

Low rate of proliferation in immature thymocytes of the non-obese diabetic mouse maps to the Idd6 diabetes susceptibility region

AIMS/HYPOTHESIS

The non-obese diabetic (NOD) mouse spontaneously develops T-cell-dependent autoimmune diabetes. This mouse strain has a number of immune dysfunctions related to T-cell development but so far there are no available data on the proliferation of NOD immature thymocytes. We therefore studied the thymocyte proliferation in the NOD mouse in discrete stages of T-cell development.

METHODS

We depleted thymocytes in vivo and analysed thymocyte proliferation during the thymus recovery from depletion. We used co-segregation analysis and quantitative loci trait analysis to investigate the genetic control of proliferation impairments in NOD thymocytes.

RESULTS

Immature thymocytes of female NOD mice proliferate with a relatively low rate compared to non-autoimmune C57Bl/6 mice. This aberrant proliferation was most pronounced in CD4-/lo CD8+ cells differentiating from the CD4-CD8- to the CD4+CD8+ stage. A genetic mapping study using an F2 intercross between the NOD and the C57BL/6 strains showed that a major locus controlling this trait is linked to the insulin-dependent diabetes susceptibility locus Idd6.

CONCLUSION/INTERPRETATION

Our results suggest that impairment of proliferation of immature thymocytes is one possible mechanism through which the Idd6 locus contributes to the pathogenesis of diabetes.

CTLA-4-/- mice display T cell-apoptosis resistance resembling that ascribed to autoimmune-prone non-obese diabetic (NOD) mice

The genes conferring susceptibility to autoimmune (insulin-dependent) diabetes mellitus (IDDM) are, in most cases, not defined. Among the loci so far identified as associated with murine IDDM (Idd1-19), only the nature of Idd1 has been assessed. Here we show that thymocytes and peripheral lymphocytes of the non-obese diabetic (NOD) mouse are relatively resistant to apoptosis induced by gamma-irradiation. By linkage analysis of F2 progeny mice, we map this trait to a locus on chromosome 1 containing the Idd5 diabetes susceptibility region. By the use of congenic mice, we confirm the linkage data and map this locus to a 6 cM region on proximal chromosome 1. Ctla4, being localized in this chromosomal region and mediating crucial functions in T cell biology, is a logical candidate gene in the Idd5 susceptibility region. In line with this, we demonstrate that T cells from Ctla4(-/-)deficient mice show a similar resistance to gamma-irradiation-induced apoptosis as observed in the NOD mice. This reinforces the notion that CTLA-4 contributes to the pathogenesis of autoimmune diabetes.

Isolation of self antigen-reactive cells from inflamed islets of nonobese diabetic mice using CD4high expression as a marker

The low precursor frequency of Ag-reactive CD4+ T cells has been a barrier to the study of CD4+ T cell responses to conventional Ags as well as CD4+ T cell responses to autoantigens recognized during the course of an autoimmune disease. We have recently reported that all "conventional Ag" reactive CD4+ T cells are contained within the subpopulation expressing high levels of the CD4 molecule, termed CD4high. We have identified a CD4high population in the islets of Langerhans of prediabetic nonobese diabetic (NOD) mice that is extremely potent in transferring disease. As few as 500 CD4high islet-infiltrating CD4+ T cells transferred insulin-dependent diabetes mellitus to CD8 reconstituted NOD-SCID mice within 30 days of transfer. In contrast, CD4high T cells isolated from either NOD spleen or salivary glands did not transfer insulin-dependent diabetes mellitus into similar CD8-reconstituted NOD-SCID recipients. These data indicate that the precursor frequency of NOD islet-reactive, pathogenic CD4+ T cells is much higher in the prediabetic NOD pancreas than in these other organs. The islet-infiltrating CD4high T cells displayed selected memory markers, by cell surface analysis, and displayed a Th 1 phenotype by RNase protection assay, but had a marked decrease in IL-4 mRNA determined by quantitative real time PCR when compared with the less pathogenic CD4normal islet-infiltrating T cells. Use of the CD4high marker to select Ag activated T cells represents a tool to isolate and study pathogenic CD4+ T cells from autoimmune lesions in which the Ag has not been previously defined.

Diabetes induction in C57BL/6 mice reconstituted with lymphocytes of nonobese diabetic <--> C57BL/6 mouse embryo aggregation chimeras

To determine whether the genetic background of the insulin-producing beta cells of the pancreas contributes to autoimmune diabetes susceptibility, we have used a model of the disease based on transferring spleen cells from nonobese diabetic (NOD) <--> C57BL/6 (B6) embryo aggregation (EA) chimeras into B6 and NOD irradiated mice. Insulitis and diabetes could be induced into both B6 and NOD hosts, albeit with low incidence. Cyclophosphamide (CY) treatment, known to accelerate diabetes in prediabetic NOD mice, was found to increase diabetes incidence up to 50-60% in both B6 and NOD mice reconstituted with chimeric splenocytes, while diabetes did not occur in CY-treated B6 mice reconstituted with B6 splenocytes. We conclude that the genetic make-up of the target organ does not affect the final stage of the pathogenesis of insulin-dependent diabetes mellitus.

Induction of diabetes in NOD<-->C57BL/6 embryo aggregation chimeras by cyclophosphamide through preferential depletion of C57BL/6 lymphocytes

The majority of embryo aggregation (EA) mouse chimeras between non-obese diabetic (NOD) mice and C57BL/6 (B6) mice show clear signs of insulitis frequently accompanied by beta-cell destruction. Less than 5% of these chimeras, however, spontaneously progress to autoimmune diabetes, an incidence far lower than observed in NOD mice. The resistance in chimeras can be accounted for by the target organ chimerism and/or the immune system chimerism. To investigate the mechanism(s) controlling diabetes resistance in these mice, we studied a total of 92 NOD<-->B6 EA chimeras that showed overt lymphoid chimerism and treated 34 chimeras with cyclophosphamide (CY), a compound known to precipitate an acute form of insulin-dependent diabetes mellitus (IDDM) in pre-diabetic NOD mice, by interfering with regulatory mechanisms. We found that CY-treated EA chimeras displayed an increase in the NOD:B6 lymphocyte ratio and 32% of them developed diabetes that could be adoptively transferred to irradiated NOD or NOD-rag-2-/- mice. These findings suggest that lymphocyte chimerism rather than beta-cell chimerism accounts for diabetes resistance in NOD<-->B6 EA chimeras and that the susceptibility to CY-induced diabetes may be related to the proportion of NOD versus B6 lymphoid cells.

Establishment and characterization of RAG-2 deficient non-obese diabetic mice

The authors have established a new immunodeficient mouse strain on the genetic background of the diabetes prone non-obese diabetic (NOD) mouse. A deletion mutant of the RAG-2 gene was back crossed 10 generations onto the NOD/Bom strain background. The homozygous NODrag-2-/- mice lack functionally mature B and T lymphocytes and do not develop insulitis or diabetes throughout life. In contrast, heterozygous NODrag-2+/- develop both insulitis and diabetes with an incidence similar to the wild type NOD mice. In transfer experiments, spleen cells from diabetic NOD donors were found to transfer disease to NODrag-2-/- recipients similar to what has been previously observed in transfer to irradiated NOD recipients or to immunodeficient NOD-scid/scid mice. While resembling the recently established NOD-scid/scid mice in many respects, the NODrag-2-/- mice represents an advantageous model for reconstitution of the pathogenesis of murine IDDM as it does not produce any endogenous, mature T or B lymphocytes.

Programmed cell death in the pathogenesis of murine IDDM: resistance to apoptosis induced in lymphocytes by cyclophosphamide

The non-obese diabetic (NOD) mouse displays several immune related defects, each of which could potentially contribute to the immunopathogenesis of diabetes that spontaneously develops in these mice. The reported resistance of NOD-lymphocytes to several apoptosis-inducing signals constitutes one such factor. Apoptosis plays a key role in the homeostasis of the immune system, as a means of selecting lymphocyte repertoires both in primary lymphoid organs and in the periphery; distortions in the apoptotic machinery may therefore be hypothesized to be implicated in the pathogenesis of autoimmune disorders. We now report that cyclophosphamide constitutes an apoptosis signal to peripheral lymphocytes and we provide evidence that NOD B cells as well as both CD4 and CD8 T cells display resistance to cyclophosphamide-induced apoptosis. These observations support the notion that apoptosis resistance in NOD mice exists at various levels, and suggest that the CY-sensitive lymphoid population, believed to play an important role in inhibiting the disease in diabetes resistant NOD mice (particularly males), may be controlled by mechanisms that are mediated by apoptosis.