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 patientspecific 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. multiple sclerosis | oligoclonal bands | proteomics | transcriptomics | autoantigens M ultiple sclerosis (MS) is a severe inflammatory disease of the central nervous system (CNS) with a presumed autoimmune pathogenesis (1-4). Oligoclonal bands (OCBs) (5-7) of the cerebrospinal fluid (CSF) are the only established immunological biomarker of MS that has a diagnostic and prognostic relevance. OCBs are expanded Ig species that contain abundant somatic hypermutations, supposedly in response to sustained antigen stimulation (8-14). They are visualized by analytical immunoblotting on isoelectric focusing (IEF) gels, but so far, no particular target antigens could be assigned to distinct OCBs (15), because OCB quantities in diagnostic lumbar punctures are too low for direct antigen searches using biochemical techniques. Furthermore, OCBs are superimposed on a background of polyclonal antibodies, precluding differentiation between signals from OCB and background antibodies. Antibody cloning from single CSF B cells (16,17) is an elegant approach for obtaining matching heavy (H) to light (L) chains of antibodies, but it is impossible to know whether a particular antibody relates to an OCB or to the polyclonal background. Candidate target antigens detected with unfractionated CSF or with recombinant antibodies cloned from single CSF-resident B cells included lipids, proteins, combinatorial peptides, and viral products ...

Background:In a rare case of human autoimmune myositis, muscle fibers are attacked by ␥␦-T cells. Results: We identified several antigens recognized by the ␥␦-T cell receptor. Conclusion:The ␥␦-T cell receptor recognized human tRNA synthetases known as antigens of autoantibodies in myositis. Significance: This is the first report of an antigen recognized by human ␥␦-T cells in an autoimmune disease.