Recombinant Human Proteoglycan Aggrecan-G1 Domain-induced Arthritis (GIA) Mouse Model.

The recombinant human proteoglycan aggrecan-G1 domain (rhG1)-induced arthritis (GIA) mouse model is a complex model of rheumatoid arthritis (RA). In GIA, autoimmune arthritis is induced by repeated intraperitoneal immunization of genetically susceptible BALB/c mice with the rhG1 antigen emulsified in the adjuvant dimethyldioctadecylammonium (DDA). This article describes the steps for producing and purifying the rhG1 antigen, the immunization protocol, methods for following the clinical picture of arthritis, and the evaluation of relevant laboratory parameters. In this model, the autoimmune arthritis develops stepwise, similar to RA: First is the preclinical stage (after the first immunization, days 0-20) with no sign of inflammation but detectable T and B cell activation; next, the stage of early arthritis (after the second immunization, days 21-41), where the first definitive signs of arthritis appear together with autoantibody production; and then the severe late-stage arthritis (after the third immunization, after day 42), which presents with massive inflammation of the limbs, leading to cartilage and bone destruction and finally ankylosis. The protocols described here provide sufficient information for investigators to use the GIA model to study different aspects of autoimmune arthritis. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Induction of recombinant human proteoglycan aggrecan-G1 domain (rhG1)-induced arthritis (GIA) Support Protocol 1: Production of rhG1-Xa-mFc2a fusion protein with CHOK1 mammalian expression system Support Protocol 2: Purification of the rhG1-Xa-mFc2a fusion protein by affinity chromatography Support Protocol 3: Preparation of DDA adjuvant Support Protocol 4: Clinical assessment of arthritis Support Protocol 5: Measurement of serum antibody levels and cytokines Support Protocol 6: Measurement of rhG1-induced proliferation and cytokine production in spleen cell culture Support Protocol 7: Histological assessment of arthritic limbs Support Protocol 8: Evaluation of arthritis with micro-computed tomography.

Splenectomy at early stage of autoimmune arthritis delayed inflammatory response and reduced joint deterioration in mice.

The spleen plays a role in innate and adaptive immunity, and autoimmune diseases like rheumatoid arthritis (RA). We investigated the effect of splenectomy in early and moderate stages of autoimmune arthritis in a mouse model. To induce recombinant human G1-induced arthritis (GIA), BALB/c mice were immunized intraperitoneally three times in 4-week intervals with the rhG1 antigen. Mice were splenectomized on day 7 (SPE1) or day 35 (SPE2) after the initiation of immunization; tested for clinical severity, joint radiological and histological changes, serum levels of inflammatory cytokines and autoantibodies, and rhG1-specific immune responses; and compared to those in control mice with spleen left intact. Circulating Tregs and T-helper subset ratios in the spleen and inguinal lymph nodes (LNs) were also examined using flow cytometry. The onset of severe inflammatory response was significantly delayed in SPE1 and SPE2 groups compared to control mice at early stages of GIA, which was associated with increased circulating Tregs. After the third immunization, as disease progressed, the severity scores were robustly increased in all mice. Nevertheless, in splenectomized mice, we observed reduced joint deterioration and cartilage damage, more Th2 cells in LNs, and reduced levels of pro-inflammatory cytokines and autoantibodies in their sera. Mesenteric LN cells of splenectomized mice exhibited weaker response in vitro against the rhG1 antigen compared to control mice spleen. In conclusion, splenectomy in the early stages of GIA delayed the inflammatory response, suggesting a protective effect against the development and progression of severe destructive arthritis.

Natural and Pathological Autoantibodies Show Age-Related Changes in a Spontaneous Autoimmune Mouse (NZB) Model.

The natural autoantibody (natAAb) network is thought to play a role in immune regulation. These IgM antibodies react with evolutionary conserved antigens; however, they do not lead to pathological tissue destruction as opposed to pathological autoantibodies (pathAAb). The exact relation between the natAAbs and pathAAbs is still not completely understood; therefore, in the present study, we set out to measure nat- and pathAAb levels against three conserved antigens in a spontaneous autoimmune disease model: the NZB mouse strain which develops autoimmune hemolytic anemia (AIHA) from six months of age. There was an age dependent increase in the natAAb levels in the serum against Hsp60, Hsp70, and the mitochondrial citrate synthase until 6-9 months of age, followed by a gradual decrease. The pathological autoantibodies appeared after six months of age, which corresponded with the appearance of the autoimmune disease. The changes in nat/pathAAb levels were coupled with decreasing B1- and increasing plasma cell and memory B cell percentages. Based on this, we propose that there is a switch from natAAbs towards pathAAbs in aged NZB mice.

Splenectomy modulates the immune response but does not prevent joint inflammation in a mouse model of RA.

The spleen is the largest secondary lymphoid organ which is involved in the development of B cells and also in systemic (auto)immune responses. Using the recombinant human G1 domain-induced arthritis (GIA) model in splenectomized and control BALB/c mice, we investigated the role of the spleen in the induction and pathogenesis of autoimmune arthritis. Splenectomized mice developed GIA with a similar clinical picture to the control group. However, we observed significant alterations in the humoral and cellular immune responses in splenectomized mice. In the sera of the splenectomized mice, we found lower pro-inflammatory cytokine and anti-rhG1 IgM levels, but higher IL-4, anti-rhG1 IgG1 and anti-CCP and RF antibodies. The arthritis induction in the splenectomized group was associated with a significant expansion of activated helper T cells and an increase in the proportion of the circulating B1 and marginal zone B cell subsets. Importantly, immunization of the splenectomized mice with rhG1 induced the formation of germinal centers in the inguinal- and mesenteric lymph nodes (i/mLNs) which showed an active immune response to rhG1. Finally, both B and T cells from the mLNs of the splenectomized mice showed decreased intracellular Ca2+ signaling than those of the control group. Collectively, these findings indicate that the presence of the spleen is not critical for the induction of GIA, and in its absence the autoimmune arthritis is most likely promoted through the compensatory activity of the i/mLNs. However, our data implies the immunological role of the spleen in arthritis which could be further assessed in human RA.

Prolonged treatment with the proteasome inhibitor MG-132 induces apoptosis in PC12 rat pheochromocytoma cells.

Rat pheochromocytoma (PC12) cells were treated with the proteasome inhibitor MG-132 and morphological changes were recorded. Initially, neuronal differentiation was induced but after 24 h signs of morphological deterioration became apparent. We performed nuclear staining, flow cytometry and WST-1 assay then analyzed signal transduction pathways involving Akt, p38 MAPK (Mitogen-Activated Protein Kinase), JNK (c-Jun N-terminal Kinase), c-Jun and caspase-3. Stress signaling via p38, JNK and c-Jun was active even after 24 h of MG-132 treatment, while the survival-mediating Akt phosphorylation declined and the executor of apoptosis (caspase-3) was activated by that time and apoptosis was also observable. We examined subcellular localization of stress signaling components, applied kinase inhibitors and dominant negative H-Ras mutant-expressing PC12 cells in order to decipher connections of stress-mediating pathways. Our results are suggestive of that treatment with the proteasome inhibitor MG-132 has a biphasic nature in PC12 cells. Initially, it induces neuronal differentiation but prolonged treatments lead to apoptosis.

Presence of TRPA1 Modifies CD4+/CD8+ T Lymphocyte Ratio and Activation.

Transient Receptor Potential Ankyrin 1 (TRPA1) has been reported to influence neuroinflammation and lymphocyte function. We analysed the immune phenotype and activation characteristics of TRPA1-deficient mice (knockout-KO) generated by targeted deletion of the pore-loop domain of the ion channel. We compared TRPA1 mRNA and protein expression in monocyte and lymphocyte subpopulations isolated from primary and secondary lymphatic organs of wild type (WT) and KO mice. qRT-PCR and flow cytometric studies indicated a higher level of TRPA1 in monocytes than in lymphocytes, but both were orders of magnitude lower than in sensory neurons. We found lower CD4+/CD8+ thymocyte ratios, diminished CD4/CD8 rates, and B cell numbers in the KO mice. Early activation marker CD69 was lower in CD4+ T cells of KO, while the level of CD8+/CD25+ cells was higher. In vitro TcR-mediated activation did not result in significant differences in CD69 level between WT and KO splenocytes, but lower cytokine (IL-1ß, IL-6, TNF-α, IL-17A, IL-22, and RANTES) secretion was observed in KO splenocytes. Basal intracellular Ca2+ level and TcR-induced Ca2+ signal in T lymphocytes did not differ significantly, but interestingly, imiquimod-induced Ca2+ level in KO thymocytes was higher. Our results support the role of TRPA1 in the regulation of activation, cytokine production, and T and B lymphocytes composition in mice.

Regulatory T cells are less sensitive to glucocorticoid hormone induced apoptosis than CD4+ T cells.

Earlier we have reported that thymic regulatory T cells (Treg) are resistant to in vivo glucocorticoid hormone (GC)-induced apoptosis, while the most GC-sensitive DP thymocytes died through the activation of mitochondrial apoptotic pathway. Here we analyzed the apoptosis-inducing effect of high dose (10-6 M) in vitro dexamethasone (DX) treatment in mouse thymic- and splenic Tregs and CD4+ T cells. Activation of both extrinsic and intrinsic apoptotic pathways started after 2 h of DX treatment in CD4 SP thymocytes and was 3 × higher than in CD4+ splenocytes, while in Treg cells, weak activation of the extrinsic apoptotic pathway started only after 3 h. We also investigated the expression of 21 apoptosis-related molecules using a protein array and found higher level of both pro-and anti-apoptotic molecules in Tregs compared to CD4+ T cells. 4 h in vitro DX treatment induced upregulation of most apoptosis-related molecules both in Tregs and CD4+ T cells, except for the decrease of Bcl-2 expression in CD4+ T cells. We found high basal cytosolic Ca2+ levels in untreated Treg cells, which further increased after DX treatment, while the specific TCR-induced Ca2+ signal was lower in Tregs than in CD4+ T cells. Our results suggest that in the background of the relative apoptosis resistance of Treg cells to GCs might be their high basal cytosolic Ca2+ level and upregulated Bcl-2 expression. In contrast, downregulation of Bcl-2 expression in CD4+ T cells can explain their higher, DX-induced apoptosis sensitivity.

Ameliorated Autoimmune Arthritis and Impaired B Cell Receptor-Mediated Ca2+ Influx in Nkx2-3 Knock-out Mice.

B cells play a crucial role in the pathogenesis of rheumatoid arthritis. In Nkx2-3-deficient mice (Nkx2-3-/-) the spleen's histological structure is fundamentally changed; therefore, B cell homeostasis is seriously disturbed. Based on this, we were curious, whether autoimmune arthritis could be induced in Nkx2-3-/- mice and how B cell activation and function were affected. We induced arthritis with immunization of recombinant human proteoglycan aggrecan G1 domain in Nkx2-3-/- and control BALB/c mice. We followed the clinical picture, characterized the radiological changes, the immune response, and intracellular Ca2+ signaling of B cells. Incidence of the autoimmune arthritis was lower, and the disease severity was milder in Nkx2-3-/- mice than in control BALB/c mice. The radiological changes were in line with the clinical picture. In Nkx2-3-/- mice, we measured decreased antigen-induced proliferation and cytokine production in spleen cell cultures; in the sera, we found less anti-CCP-IgG2a, IL-17 and IFNγ, but more IL-1ß, IL-4 and IL-6. B cells isolated from the lymph nodes of Nkx2-3-/- mice showed decreased intracellular Ca2+ signaling compared to those isolated from BALB/c mice. Our findings show that the transcription factor Nkx2-3 might regulate the development of autoimmune arthritis most likely through modifying B cell activation.

Comparative analysis of abdominal fluid cytokine levels in ovarian hyperstimulation syndrome (OHSS).

BACKGROUND: Ovarian hyperstimulation syndrome (OHSS) is a rare, yet severe, iatrogenic complication of ovulation induction therapy during assisted reproductive procedures. Our group previously detected atypical cells in the ascitic fluid of OHSS patients, although no malignancy developed during follow up. Here, the aim was to perform a comparative analysis of the cytokines present in the abdominal fluid of patients affected by OHSS versus patients with advanced ovarian cancer, a benign adnexal mass, or ovarian endometriosis. METHODS: This prospective, non-randomized study was conducted at the Clinical Center of the University of Pecs Department of Obstetrics and Gynecology/Reproductive Center between October 2016 and March 2018. Abdominal fluid samples were obtained from 76 patients and subjected to Luminex analysis. The samples were collected from patients with OHSS (OHSS; n = 16), advanced ovarian cancer (OC; n = 22), a benign adnexal mass (BAM; n = 21), or ovarian endometriosis (EM; n = 17). Data were subjected to the non-parametric Kruskal-Wallis test and Spearman's rank correlation coefficient to identify statistical differences between the four study groups. RESULTS: Leukocytosis and hemoconcentration were detected in the peripheral blood of OHSS patients. Abdominal fluid analysis further revealed significantly higher levels of interleukin (IL)-6, IL-8, IL-10, and transforming growth factor (TGF)-ß in both the OHSS and OC groups compared to the BAM and EM groups. The highest concentration of vascular endothelial growth factor (VEGF) was detected in the OC group, while a significantly lower level was detected in the OHSS group. Moreover, VEGF levels in OC and OHSS groups were significantly elevated compared to the levels in the BAM and EM groups. CONCLUSIONS: Vasoactive and hematogenic cytokines were present at higher levels in both the OHSS and OC abdominal fluid samples compared to the fluid samples obtained from the peritoneal cavity of the BAM patients. It is possible that these cytokines play an important role in the formation of ascites.

ZAP-70 Regulates Autoimmune Arthritis via Alterations in T Cell Activation and Apoptosis.

T cells play an essential role in the pathogenesis of both human rheumatoid arthritis (RA) and its murine models. A key molecule in T cell activation is ZAP-70, therefore we aimed to investigate the effects of partial ZAP-70 deficiency on the pathogenesis of recombinant human G1(rhG1)-induced arthritis (GIA), a well-established mouse model of RA. Arthritis was induced in BALB/c and ZAP-70+/- heterozygous mice. Disease progression was monitored using a scoring system and in vivo imaging, antigen-specific proliferation, cytokine and autoantibody production was measured and T cell apoptotic pathways were analyzed. ZAP-70+/- mice developed a less severe arthritis, as shown by both clinical picture and in vitro parameters (decreased T cell proliferation, cytokine and autoantibody production). The amount of cleaved Caspase-3 increased in arthritic ZAP-70+/- T cells, with no significant changes in cleaved Caspase-8 and -9 levels; although expression of Bim, Bcl-2 and Cytochrome C showed alterations. Tyrosine phosphorylation was less pronounced in arthritic ZAP-70+/- T cells and the amount of Cbl-b-a negative regulator of T cell activation-decreased as well. We hypothesize that the less severe disease seen in the partial absence of ZAP-70 might be caused by the decreased T cell activation accompanied by increased apoptosis.

Regulatory role of capsaicin-sensitive peptidergic sensory nerves in the proteoglycan-induced autoimmune arthritis model of the mouse.

OBJECTIVE: The regulatory role of capsaicin-sensitive peptidergic sensory nerves has been shown in acute inflammation, but little is known about their involvement in T/B-cell driven autoimmune arthritis. This study integratively characterized the function of these nerve endings in the proteoglycan-induced chronic arthritis (PGIA), a translational model of rheumatoid arthritis. METHODS: Peptidergic afferents were defunctionalized by resiniferatoxin (RTX) pretreatment in BALB/c mice, PGIA was induced by repeated antigen challenges. Hind paw volume, arthritis severity, grasping ability and the mechanonociceptive threshold were monitored during the 17-week experiment. Myeloperoxidase activity, vascular leakage and bone turnover were evaluated by in vivo optical imaging. Bone morphology was assessed using micro-CT, the intertarsal small joints were processed for histopathological analysis. RESULTS: Following desensitization of the capsaicin-sensitive afferents, ankle edema, arthritis severity and mechanical hyperalgesia were markedly diminished. Myeloperoxidase activity was lower in the early, but increased in the late phase, whilst plasma leakage and bone turnover were not altered. Desensitized mice displayed similar bone spurs and erosions, but increased trabecular thickness of the tibia and bony ankylosis of the spine. Intertarsal cartilage thickness was not altered in the model, but desensitization increased this parameter in both the non-arthritic and arthritic groups. CONCLUSION: This is the first integrative in vivo functional and morphological characterization of the PGIA mouse model, wherein peptidergic afferents have an important regulatory function. Their overall effect is proinflammatory by increasing acute inflammation, immune cell activity and pain. Meanwhile, their activation decreases spinal ankylosis, arthritis-induced altered trabecularity, and cartilage thickness in small joints.

Glucocorticoid hormone treatment enhances the cytokine production of regulatory T cells by upregulation of Foxp3 expression.

OBJECTIVE: Despite the fact that glucocorticoids (GC) are important therapeutic tools, their effects on regulatory T cells (Treg) are not well defined. The aim of our work was to investigate how GCs influence in vivo the thymic (tTreg) and peripheral Treg (pTreg) differentiation, survival and cytokine production. METHODS: Tregs were detected with flow cytometry in lymphatic organs of 4-6 weeks old BALB/c mice after repeated (2-4days), high-dose in vivo GC treatment using CD4/CD25 cell surface and Foxp3/IL-10/TGFß/glucocorticoid receptor (GR) intracellular staining. Cytokine, Foxp3, and GR mRNA levels of sorted CD4+CD25high T cells were analyzed using RT-PCR. Foxp3 and GR localization in Treg cells was investigated with confocal microscopy. RESULTS: GC treatment of mice resulted in increased relative tTreg frequency in the thymus, which was due to decreased total thymocyte numbers with unchanged absolute tTreg cell count. In contrast the relative pTreg cell ratio in secondary lymphatic organs decreased or showed no changes after GC treatment, while the absolute number of pTregs decreased. Elevated intracellular IL-10+ and TGFß+ tTreg and pTreg ratios were measured in GC-treated animals, accompanied with elevated Foxp3 mRNA expression. In addition, GC treatment caused increased TGFß and IL-35 mRNA expression in CD4+CD25high+ splenic and elevated IL-10 mRNA level in thymic tTregs. GR expression of thymic tTreg cells was lower than in pTregs. GC treatment caused an opposite change in GR levels, elevating GR in tTregs but decreasing it in pTregs. We observed a nuclear localization of GR in both tTregs and pTregs, which showed high colocalization (∼60%) with Foxp3 transcription factor. These data suggest an interaction of these two transcription factors with further increase due to GC treatment in splenic pTregs. CONCLUSION: Our data show selective survival of tTregs and elevated production of immunosuppressive cytokines by Treg cells after GC treatment, which may contribute to the immunosuppressive effects of GCs.

The regulation of the mitochondrial apoptotic pathway by glucocorticoid receptor in collaboration with Bcl-2 family proteins in developing T cells.

Glucocorticoids (GC) are important in the regulation of selection and apoptosis of CD4+CD8+ double-positive (DP) thymocytes. The pronounced GC-sensitivity of DP thymocytes, observed earlier, might be due to the combination of classical (genomic) and alternative (non-genomic) glucocorticoid receptor (GR) signaling events modifying activation or apoptotic pathways. In particular, the previously demonstrated mitochondrial translocation of activated GR in DP thymocytes offered a fascinating explanation for their pronounced GC-induced apoptosis sensitivity. However, the fine molecular details how the mitochondrial translocation of GR might regulate apoptosis remained unclear. Therefore, in the present study, we intended to examine which apoptotic pathways could be involved in GC-induced thymocyte apoptosis. Furthermore we investigated the potential relationship between the GR and Bcl-2 proteins. Using an in vitro test system, thymocytes from 4-week-old BALB/c mice, were treated with the GC-analogue dexamethasone (DX). Bax accumulated in mitochondria upon DX treatment. Mitochondrial GR showed association with members of the Bcl-2 family: Bak, Bim, Bcl-xL. Elevated Cytochrome C, and active caspase-3, -8, and -9 levels were detected in thymocytes after DX treatment. These results support the hypothesis that in early phases of GC-induced thymocyte apoptosis, the mitochondrial pathway plays a crucial role, confirmed by the release of Cytochrome C and the activation of caspase-9. The activation of caspase-8 was presumably due to cross-talk between apoptotic signaling pathways. We propose that the GC-induced mitochondrial accumulation of Bax and the interaction between the GR and Bim, Bcl-xL and Bak could play a role in the regulation of thymocyte apoptosis.

FTY720 (Gilenya) treatment prevents spontaneous autoimmune myocarditis and dilated cardiomyopathy in transgenic HLA-DQ8-BALB/c mice.

Although dilated cardiomyopathy (DCM) is often caused by viral infections, it frequently involves autoimmune mechanisms associated with particular HLA-DR and DQ alleles. Our homozygous HLA-DQ8Ab(0) transgenic mice in the BALB/c background (HLA-DQ8(BALB/c)-Tg) developed early and progressive fatal heart failure from 4 to 5 weeks of age. Clinical signs of the disease included cyanotic eyes, tachycardia with dyspnea (from pale to cyanotic limbs), and terminal whole body edema. Sick mice had extremely dilated hearts, enlarged liver and spleen, and pleural/peritoneal effusion. Histology of the heart showed extensive heart muscle destruction with signs of fibrosis. The autoimmune nature of the disease was shown by high titers of antimyosin antibodies in the sera and IgG deposits in sick heart muscles, as well as focal neutrophil, T cell, and macrophage infiltration of the heart muscle. The sera of the sick mice showed a granular staining pattern on sections of healthy heart muscle. Quantitative analyses of DCM-specific gene expression studies revealed that sets of genes are involved in inflammation, hypoxia, and fibrosis. Treatment with FTY720 (Fingolimod/Gilenya) protected animals from the development of cardiomyopathy. HLA-DQ8(BALB/c)-Tg mice represent a spontaneous autoimmune myocarditis model that may provide a useful tool for studying the autoimmune mechanism of DCM and testing immunosuppressive drugs.

Enigma of IL-17 and Th17 Cells in Rheumatoid Arthritis and in Autoimmune Animal Models of Arthritis.

Rheumatoid arthritis (RA) is one of the most common autoimmune disorders characterized by the chronic and progressive inflammation of various organs, most notably the synovia of joints leading to joint destruction, a shorter life expectancy, and reduced quality of life. Although we have substantial information about the pathophysiology of the disease with various groups of immune cells and soluble mediators identified to participate in the pathogenesis, several aspects of the altered immune functions and regulation in RA remain controversial. Animal models are especially useful in such scenarios. Recently research focused on IL-17 and IL-17 producing cells in various inflammatory diseases such as in RA and in different rodent models of RA. These studies provided occasionally contradictory results with IL-17 being more prominent in some of the models than in others; the findings of such experimental setups were sometimes inconclusive compared to the human data. The aim of this review is to summarize briefly the recent advancements on the role of IL-17, particularly in the different rodent models of RA.

Wnt-4 protects thymic epithelial cells against dexamethasone-induced senescence.

Glucocorticoids are widely used immunosuppressive drugs in treatment of autoimmune diseases and hematological malignancies. Glucocorticoids are particularly effective immune suppressants, because they induce rapid peripheral T cell and thymocyte apoptosis resulting in impaired T cell-dependent immune responses. Although glucocorticoids can induce apoptotic cell death directly in developing thymocytes, how exogenous glucocorticoids affect the thymic epithelial network that provides the microenvironment for T cell development is still largely unknown. In the present work, we show that primary thymic epithelial cells (TECs) express glucocorticoid receptors and that high-dosage dexamethasone induces degeneration of the thymic epithelium within 24 h of treatment. Changes in organ morphology are accompanied by a decrease in the TEC transcription factor FoxN1 and its regulator Wnt-4 parallel with upregulation of lamina-associated polypeptide 2α and peroxisome proliferator activator receptor γ, two characteristic molecular markers for adipose thymic involution. Overexpression of Wnt-4, however, can prevent upregulation of adipose differentiation-related aging markers, suggesting an important role of Wnt-4 in thymic senescence.

Proteoglycan-induced arthritis and recombinant human proteoglycan aggrecan G1 domain-induced arthritis in BALB/c mice resembling two subtypes of rheumatoid arthritis.

OBJECTIVE: To develop a simplified and relatively inexpensive version of cartilage proteoglycan-induced arthritis (PGIA), an autoimmunity model of rheumatoid arthritis (RA), and to evaluate the extent to which this new model replicates the disease parameters of PGIA and RA. METHODS: Recombinant human G1 domain of human cartilage PG containing "arthritogenic" T cell epitopes was generated in a mammalian expression system and used for immunization of BALB/c mice. The development and progression of arthritis in recombinant human PG G1-immunized mice (designated recombinant human PG G1-induced arthritis [GIA]) was monitored, and disease parameters were compared with those in the parent PGIA model. RESULTS: GIA strongly resembled PGIA, although the clinical symptoms and immune responses in mice with GIA were more uniform than in those with PGIA. Mice with GIA showed evidence of stronger Th1 and Th17 polarization than those with PGIA, and anti-mouse PG autoantibodies were produced in different isotype ratios in the 2 models. Rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies were detected in both models; however, serum levels of IgG-RF and anti-CCP antibodies were different in GIA and PGIA, and both parameters correlated better with disease severity in GIA than in PGIA. CONCLUSION: GIA is a novel model of seropositive RA that exhibits all of the characteristics of PGIA. Although the clinical phenotypes are similar, GIA and PGIA are characterized by different autoantibody profiles, and the 2 models may represent 2 subtypes of seropositive RA, in which more than 1 type of autoantibody can be used to monitor disease severity and response to treatment.

Impaired activation-induced cell death promotes spontaneous arthritis in antigen (cartilage proteoglycan)-specific T cell receptor-transgenic mice.

OBJECTIVE: To investigate whether genetic preponderance of a T cell receptor (TCR) recognizing an arthritogenic peptide of human cartilage proteoglycan (PG) is sufficient for development of arthritis. METHODS: We performed a longitudinal study using BALB/c mice expressing a TCR that recognizes the arthritogenic ATEGRVRVNSAYQDK peptide of human cartilage PG. PG-specific TCR-transgenic (PG-TCR-Tg) mice were inspected weekly for peripheral arthritis until 12 months of age. Peripheral joints were examined histologically, and T cell responses, T cell activation markers, serum cytokines, and autoantibodies were measured. Apoptosis and signaling studies were performed in vitro on T cells from aged PG-TCR-Tg mice. RESULTS: Spontaneous arthritis developed as early as 5-6 months of age, and the incidence increased to 40-50% by 12 months of age. Progressive inflammation began with cartilage and bone erosions in the interphalangeal joints, and later expanded to the proximal joints of the front and hind paws. Spontaneous arthritis was associated with a high proportion of activated CD4+ T cells, enhanced interferon-γ and interleukin-17 (IL-17) production, and elevated levels of serum autoantibodies. PG-TCR-Tg mice lacking IL-4 developed arthritis earlier and at a higher incidence than IL-4-sufficient mice. Antigen-specific activation-induced cell death was diminished in vitro in CD4+ T cells of PG-TCR-Tg mice with spontaneous arthritis, especially in those lacking IL-4. CONCLUSION: The presence of CD4+ T cells expressing a TCR specific for an arthritogenic PG epitope is sufficient to trigger spontaneous autoimmune inflammation in the joints of BALB/c mice. IL-4 appears to be a negative regulator of this disease, through attenuation of activation-induced cell death.

Immunosenescence and its potential modulation: lessons from mouse models.

Evaluation of: Goldmann O, Lehne S, Medina E. Age-related susceptibility to Streptococcus pyogenes infection in mice: underlying immune dysfunction and strategy to enhance immunity. J. Pathol. 220(5), 521-529 (2010). Immunosenescence is a pathophysiological event in the aging process, which probably represents the greatest danger to an individual; diminished immune functions and altered immunoregulation lead to increased susceptibility to infections, autoimmunity and increased frequency of tumors in the elderly. Immunosenescence affects the functions of both innate immune cells (such as neutrophils, macrophages and dendritic cells) and cells involved in adaptive immunity (T and B lymphocytes). A number of methods have been developed to monitor age-related abnormalities in inbred murine strains, including physiologial and immunological tests, and a variety of genetic and epigenetic assays. Various animal models enable investigation of certain aspects of the aging process, and also allow for testing of immune-modulating agents that might 'rejuvenate' the cellular functions altered by aging. Although short-term experiments with targeted compounds to replenish certain cell types or restore cellular functions may present impressive results of 'rejuvenation' of innate immunity (reduced susceptibility to an infectious agent), to date, immunosenescence still remains a phenomenological term with limited etiologic information at the cellular and molecular levels.

Emerging pathways of non-genomic glucocorticoid (GC) signalling in T cells.

In the last decade new glucocorticoid (GC)-signalling mechanisms have emerged. The evolving field of non-genomic GC actions was precipitated from two major directions: (i) some rapid/acute clinical GC applications could not be explained based on the relatively slowly appearing genomic GC action and (ii) accumulating evidence came to light about the discrepancy in the apoptosis sensitivity and GR expression of thymocytes and other lymphoid cell types. Herein, we attempt to sample the latest information in the field of non-genomic GC signalling in T cells, and correlate it with results from our laboratory. We discuss some aspects of the regulation of thymocyte apoptosis by GCs, paying special interest to the potential role(s) of mitochondrial GR signalling. The interplay between the T cell receptor (TcR) and glucocorticoid receptor (GR) signalling pathways is described in more detail, focusing on ZAP-70, which is a novel target of rapid GC action.