Eileen McMahon

Epitope spreading initiates in the CNS in two mouse models of multiple sclerosis

Chronic progression of two T cell–mediated central nervous system (CNS) demyelinating models of multiple sclerosis, relapsing EAE (R-EAE) and Theilers murine encephalomyelitis virus–induced demyelinating disease (TMEV-IDD) is dependent on the activation of T cells to endogenous myelin epitopes (epitope spreading). Using transfer of carboxyfluorescein succinyl ester (CFSE)-labeled T-cell receptor (TCR)-transgenic T cells and mixed bone marrow chimeras, we show that activation of naive proteolipid protein (PLP)139–151-specific T cells in SJL mice undergoing PLP178–191-induced R-EAE or TMEV-IDD occurs directly in the CNS and not in the cervical lymph nodes or other peripheral lymphoid organs. Examination of the antigen-presentation capacity of antigen-presenting cell (APC) populations purified from the CNS of mice with PLP178–191-induced R-EAE shows that only F4/80−CD11c+CD45hi dendritic cells (DCs) efficiently present endogenous antigen to activate naive PLP139–151-specific T cells in vitro. In contrast, DCs as well as F4/80+CD45hi macrophages and F4/80+CD45lo microglia activate a PLP139–151-specific helper T cell line. The data suggest that naive T cells enter the inflamed CNS and are activated by local APCs, possibly DCs, to initiate epitope spreading.

CNS myeloid DCs presenting endogenous myelin peptides 'preferentially' polarize CD4+ TH-17 cells in relapsing EAE

Peripherally derived CD11b+ myeloid dendritic cells (mDCs), plasmacytoid DCs, CD8α+ DCs and macrophages accumulate in the central nervous system during relapsing experimental autoimmune encephalomyelitis (EAE). During acute relapsing EAE induced by a proteolipid protein peptide of amino acids 178–191, transgenic T cells (139TCR cells) specific for the relapse epitope consisting of proteolipid protein peptide amino acids 139–151 clustered with mDCs in the central nervous system, were activated and differentiated into T helper cells producing interleukin 17 (TH-17 cells). CNS mDCs presented endogenously acquired peptide, driving the proliferation of and production of interleukin 17 by naive 139TCR cells in vitro and in vivo. The mDCs uniquely biased TH-17 and not TH1 differentiation, correlating with their enhanced expression of transforming growth factor-β1 and interleukins 6 and 23. Plasmacytoid DCs and CD8α+ DCs were superior to macrophages but were much less efficient than mDCs in presenting endogenous peptide to induce TH-17 cells. Our findings indicate a critical function for CNS mDCs in driving relapses in relapsing EAE.

Antigen Presentation in the CNS by Myeloid Dendritic Cells Drives Progression of Relapsing Experimental Autoimmune Encephalomyelitis

Abstract:  Chronic progression of relapsing experimental autoimmune encephalomyelitis (R‐EAE), a mouse model of multiple sclerosis (MS), is dependent on the activation of T cells to endogenous myelin epitopes, that is, epitope spreading. This review focuses on the cellular and molecular mechanisms underlying the process of epitope spreading. Surprisingly, activation of naïve T cells to endogenous myelin epitopes in SJL mice undergoing R‐EAE occurs directly in the central nervous system (CNS), a site generally perceived to be immunologically privileged. Determination of the antigen presentation capacity of antigen‐presenting cell (APC) populations purified from the CNS of mice with established R‐EAE shows that peripherally derived CD11b+CD11c+CD45hi myeloid dendritic cells (mDCs) most efficiently present endogenous myelin antigens to activate both preactivated effector myelin‐specific T cells and naïve T cells. The mDCs, which drive epitope spreading, preferentially polarize pathogenic Th17 responses correlating with their enhanced expression of TGF‐β1, IL‐6, and IL‐23. Both B220+CD11c+ plasmacytoid (pDCs) and CD8α+CD11c+ (CD8 DCs) were superior to CD11b+CD11c–CD45hi macrophages, but less efficient than mDCs at presenting endogenous peptide to induce Th17 cells. In contrast, CNS‐resident CD11b+CD11c–CD45low microglia purified from the inflamed CNS were found to be largely incapable of activating either naïve or effector T cells.

Interferon-γ-Oligodendrocyte Interactions in the Regulation of Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an animal model of the human demyelinating disorder multiple sclerosis (MS). The immune cytokine interferon-gamma (IFN-γ) is believed to participate in disease pathogenesis in both EAE and MS. In the present study, we examined the significance of IFN-γ-oligodendrocyte interactions in the course of EAE. For the purpose of our study, we used the previously described [proteolipid protein/suppressor of cytokine signaling 1 (PLP/SOCS1)] transgenic mouse line that displays suppressed oligodendrocyte responsiveness to IFN-γ. PLP/SOCS1 mice developed EAE with an accelerated onset associated with enhanced early inflammation and markedly increased oligodendrocyte apoptosis. Moreover, we found that IFN-γ pretreatment of mature oligodendrocytes in vitro had a protective effect against oxidative stress and the inhibition of proteasome activity and resulted in upregulation in expression of a number of chemokines, including CXCL10 (IP10), CCL2 (MCP-1), CCL3 (MCP-1α), and CCL5 (RANTES). These results suggest that IFN-γ-oligodendrocyte interactions are of significance to the clinical and pathological aspects of EAE. In addition, the present study suggests that oligodendrocytes are not simply targets of inflammatory injury but active participants of the neuroimmune network operating during the course of EAE.

Upregulation of the Stress-Associated Gene p8 in Mouse Models of Demyelination and in Multiple Sclerosis Tissues

Cuprizone‐induced demyelination is a mouse model of multiple sclerosis (MS) as cuprizone‐fed mice exhibit neuroinflammation and demyelination in the brain. Upon removal of cuprizone from the diet, inflammation is resolved and reparative remyelination occurs. In an Affymetrix GeneChip analysis, the stress‐associated gene p8 was strongly upregulated (>10×) during cuprizone‐induced demyelination but not remyelination. We verified this upregulation (>15×) of p8 in the CNS during demyelination by real‐time polymerase chain reaction (PCR). This upregulation is brain‐specific, as p8 is not elevated in the liver, lung, kidney, spleen, and heart of cuprizone‐treated mice. We also localized the cellular source of p8 during cuprizone treatment, and further found elevated expression during embryogenesis but not in normal adult brain. Compared with wild‐type controls, the death of oligodendrocytes in p8−/− mice is delayed, as is microglial recruitment to areas of demyelination. The corpus callosum of p8−/− mice demyelinates at a slower rate than wild‐type mice, suggesting that p8 exacerbates CNS inflammation and demyelination. Enhanced expression of p8 is also observed in the spinal cords of mice with acute experimental autoimmune encephalomyelitis (EAE) induced by PLP139‐151 peptide (10×). Increased expression is detected during disease onset and expression wanes during the remission phase. Finally, p8 is found upregulated (8×) in post‐mortem tissue from MS patients and is higher in the plaque tissue compared with adjacent normal‐appearing white and gray matter. Thus, p8 is an excellent candidate as a novel biomarker of demyelination.

Characterization of a novel and spontaneous mouse model of inflammatory arthritis

IntroductionMouse models of rheumatoid arthritis (RA) have proven critical for identifying genetic and cellular mechanisms of the disease. Upon discovering mice in our breeding colony that had spontaneously developed inflamed joints reminiscent of RA, we established the novel IIJ (inherited inflamed joints) strain. The purpose of this study was to characterize the histopathological, clinical, genetic and immunological properties of the disease.MethodsTo begin the IIJ strain, an arthritic male mouse was crossed with SJL/J females. Inheritance of the phenotype was then tracked by intercrossing, backcrossing and outcrossing to other inbred strains. The histopathology of the joints and extraarticular organ systems was examined. Serum cytokines and immunoglobulins (Igs) were measured by ELISA and cytometric bead array. Transfer experiments tested whether disease could be mediated by serum alone. Finally, the cellular joint infiltrate and the composition of secondary lymphoid organs were examined by immunohistochemistry and flow cytometry.ResultsAfter nine generations of intercrossing, the total incidence of arthritis was 33% (304 of 932 mice), with females being affected more than males (38% vs. 28%; P < 0.001). Swelling, most notably in the large distal joints, typically became evident at an early age (mean age of 52 days). In addition to the joint pathology, which included bone and cartilage erosion, synovial hyperproliferation and a robust cellular infiltration of mostly Gr-1+ neutrophils, there was also evidence of systemic inflammation. IL-6 was elevated in the sera of recently arthritic mice, and extraarticular inflammation was observed histologically in multiple organs. Total serum Ig and IgG1 levels were significantly elevated in arthritic mice, and autoantibodies such as rheumatoid factor and Ig reactive to joint components (collagen type II and joint homogenate) were also detected. Nevertheless, serum failed to transfer disease. A high percentage of double-negative (CD4-CD8-) CD3+ TCRα/β+ T cells in the lymphoid organs of arthritic IIJ mice suggested significant disruption in the T-cell compartment.ConclusionsOverall, these data identify the IIJ strain as a new murine model of inflammatory, possibly autoimmune, arthritis. The IIJ strain is similar, both histologically and serologically, to RA and other murine models of autoimmune arthritis. It may prove particularly useful for understanding the female bias in autoimmune diseases.