Hartmut Wekerle

The role of autoimmune T lymphocytes in the pathogenesis of multiple sclerosis

Autoimmune T cells play a key role as regulators and effectors of autoimmune disease.In multiple sclerosis (MS), activated T cells specific for myelin components or other locally expressed autoantigens enter the CNS and recognize their antigen(s) on local antigen-presenting cells. After local stimulation, the T cells produce a plethora of cytokines and inflammatory mediators that have profound effects on the local cellular environment, induce and recruit additional inflammatory cells, and contribute to myelin damage. An increasingly detailed knowledge of these processes will greatly facilitate the development of new immunotherapies. This article focuses on the role of T cells in MS. We provide a brief overview of the principles of T-cell immunology, discuss the experimental techniques available for studying T cells, address the role of T cells in the pathogenesis of MS, and highlight modern concepts for immunotherapy. NEUROLOGY 1995;45(Suppl 6): S33-S38

Distinct oligoclonal band antibodies in multiple sclerosis recognize ubiquitous self-proteins

Significance Oligoclonal bands (OCBs) of the cerebrospinal fluid (CSF) are a hallmark of multiple sclerosis (MS). They are expanded antibody species that are detectable in >95% of patients. Because several OCB and polyclonal antibodies are present in a CSF sample, it was for technical reasons thus far not possible to isolate distinct OCBs and identify their antigens. Here we combined refined biochemical analysis, proteomics, and transcriptomics to molecularly characterize distinct OCB antibodies. We produced six recombinant OCB antibodies and characterized three autoantigens. All of them were ubiquitous intracellular proteins, not specific to brain tissue. This finding indicates that in MS, part of the OCBs do not directly mediate tissue destruction, but rather, indicate a secondary immune response. Oligoclonal Ig bands (OCBs) of the cerebrospinal fluid are a hallmark of multiple sclerosis (MS), a disabling inflammatory disease of the central nervous system (CNS). OCBs are locally produced by clonally expanded antigen-experienced B cells and therefore are believed to hold an important clue to the pathogenesis. However, their target antigens have remained unknown, mainly because it was thus far not possible to isolate distinct OCBs against a background of polyclonal antibodies. To overcome this obstacle, we copurified disulfide-linked Ig heavy and light chains from distinct OCBs for concurrent analysis by mass spectrometry and aligned patient-specific peptides to corresponding transcriptome databases. This method revealed the full-length sequences of matching chains from distinct OCBs, allowing for antigen searches using recombinant OCB antibodies. As validation, we demonstrate that an OCB antibody from a patient with an infectious CNS disorder, neuroborreliosis, recognized a Borrelia protein. Next, we produced six recombinant antibodies from four MS patients and identified three different autoantigens. All of them are conformational epitopes of ubiquitous intracellular proteins not specific to brain tissue. Our findings indicate that the B-cell response in MS is heterogeneous and partly directed against intracellular autoantigens released during tissue destruction. In addition to helping elucidate the role of B cells in MS, our approach allows the identification of target antigens of OCB antibodies in other neuroinflammatory diseases and the production of therapeutic antibodies in infectious CNS diseases.

Visualizing context-dependent calcium signaling in encephalitogenic T cells in vivo by two-photon microscopy.

Significance Before invading the central nervous system, encephalitogenic T cells cross a series of microenvironments where they interact with local cells. T-cell activation was visualized by specific calcium signals using a combination of a genetic calcium reporter, Twitch1, and in vivo two-photon microscopy. In peripheral immune organs, short-lived calcium signaling indicated antigen-independent interactions. By contrast, in the CNS, saturated long-lived calcium signaling was induced by endogenous autoantigens presented by a subset of local antigen-presenting cells. Because T-cell trafficking is controlled at serial checkpoints, our findings may help to identify therapeutic targets for preventing CNS inflammation. In experimental autoimmune encephalitis (EAE), autoimmune T cells are activated in the periphery before they home to the CNS. On their way, the T cells pass through a series of different cellular milieus where they receive signals that instruct them to invade their target tissues. These signals involve interaction with the surrounding stroma cells, in the presence or absence of autoantigens. To portray the serial signaling events, we studied a T-cell–mediated model of EAE combining in vivo two-photon microscopy with two different activation reporters, the FRET-based calcium biosensor Twitch1 and fluorescent NFAT. In vitro activated T cells first settle in secondary (2°) lymphatic tissues (e.g., the spleen) where, in the absence of autoantigen, they establish transient contacts with stroma cells as indicated by sporadic short-lived calcium spikes. The T cells then exit the spleen for the CNS where they first roll and crawl along the luminal surface of leptomeningeal vessels without showing calcium activity. Having crossed the blood–brain barrier, the T cells scan the leptomeningeal space for autoantigen-presenting cells (APCs). Sustained contacts result in long-lasting calcium activity and NFAT translocation, a measure of full T-cell activation. This process is sensitive to anti-MHC class II antibodies. Importantly, the capacity to activate T cells is not a general property of all leptomeningeal phagocytes, but varies between individual APCs. Our results identify distinct checkpoints of T-cell activation, controlling the capacity of myelin-specific T cells to invade and attack the CNS. These processes may be valuable therapeutic targets.