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B cells undergo several rounds of selection to eliminate potentially pathogenic autoreactive clones, but in contrast to T cells, evidence of positive selection of autoreactive B cells remains moot. Using unique tetramers, we traced natural autoreactive B cells (C1-B) specific for a defined triple-helical epitope on collagen type-II (COL2), constituting a sizeable fraction of the physiological B cell repertoire in mice, rats, and humans. Adoptive transfer of C1-B suppressed arthritis independently of IL10, separating them from IL10-secreting regulatory B cells. Single-cell sequencing revealed an antigen processing and presentation signature, including induced expression of CD72 and CCR7 as surface markers. C1-B presented COL2 to T cells and induced the expansion of regulatory T cells in a contact-dependent manner. CD72 blockade impeded this effect suggesting a new downstream suppressor mechanism that regulates antigen-specific T cell tolerization. Thus, our results indicate that autoreactive antigen-specific naïve B cells tolerize infiltrating T cells against self-antigens to impede the development of tissue-specific autoimmune inflammation.

A longstanding goal has been to find an antigen-specific preventive therapy, i.e., a vaccine, for autoimmune diseases. It has been difficult to find safe ways to steer the targeting of natural regulatory antigen. Here, we show that the administration of exogenous mouse major histocompatibility complex class II protein bounding a unique galactosylated collagen type II (COL2) peptide (Aq-galCOL2) directly interacts with the antigen-specific TCR through a positively charged tag. This leads to expanding a VISTA-positive nonconventional regulatory T cells, resulting in a potent dominant suppressive effect and protection against arthritis in mice. The therapeutic effect is dominant and tissue specific as the suppression can be transferred with regulatory T cells, which downregulate various autoimmune arthritis models including antibody-induced arthritis. Thus, the tolerogenic approach described here may be a promising dominant antigen-specific therapy for rheumatoid arthritis, and in principle, for autoimmune diseases in general.

B cells undergo several rounds of selection to eliminate potentially pathogenic autoreactive clones, but in contrast to T cells, evidence of positive selection of autoreactive B cells remains moot. Using unique tetramers, we traced natural autoreactive B cells (C1-B) specific for a defined triple-helical epitope on collagen type-II (COL2), constituting a sizeable fraction of the physiological B cell repertoire in mice, rats, and humans. Adoptive transfer of C1-B suppressed arthritis independently of IL10, separating them from IL10-secreting regulatory B cells. Single-cell sequencing revealed an antigen processing and presentation signature, including induced expression of CD72 and CCR7 as surface markers. C1-B presented COL2 to T cells and induced the expansion of regulatory T cells in a contact-dependent manner. CD72 blockade impeded this effect suggesting a new downstream suppressor mechanism that regulates antigen-specific T cell tolerization. Thus, our results indicate that autoreactive antigen-specific naive B cells tolerize infiltrating T cells against self-antigens to impede the development of tissue-specific autoimmune inflammation.

A longstanding goal has been to find an antigen-specific preventive therapy, i.e., a vaccine, for autoimmune diseases. It has been difficult to find safe ways to steer the targeting of natural regulatory antigen. Here, we show that the administration of exog-enous mouse major histocompatibility complex class II protein bounding a unique galactosylated collagen type II (COL2) peptide (Aq-galCOL2) directly interacts with the antigen-specific TCR through a positively charged tag. This leads to expanding a VISTA-positive nonconventional regulatory T cells, resulting in a potent dominant suppressive effect and protection against arthritis in mice. The therapeutic effect is dom-inant and tissue specific as the suppression can be transferred with regulatory T cells, which downregulate various autoimmune arthritis models including antibody-induced arthritis. Thus, the tolerogenic approach described here may be a promising dominant antigen-specific therapy for rheumatoid arthritis, and in principle, for autoimmune diseases in general.

Objectives Rheumatoid arthritis (RA) is an autoimmune disease strongly associated with the major histocompatibility complex (MHC) class II allele DRB1*04:01, which encodes a protein that binds self-peptides for presentation to T cells. This study characterises the autoantigen-presenting function of DRB1*04:01 (HLA-DRA*01:01/HLA-DRB1*04:01) at a molecular level for prototypic T-cell determinants, focusing on a post-translationally modified collagen type II (Col2)-derived peptide. Methods The crystal structures of DRB1*04:01 molecules in complex with the peptides HSP70(289-306), citrullinated CILP982-996 and galactosylated Col2(259-273) were determined on cocrystallisation. T cells specific for Col2(259-273) were investigated in peripheral blood mononuclear cells from patients with DRB1*04:01-positive RA by cytofluorometric detection of the activation marker CD154 on peptide stimulation and binding of fluorescent DRB1*0401/Col2(259-273) tetramer complexes. The cDNAs encoding the T-cell receptor (TCR) alpha-chains and beta-chains were cloned from single-cell sorted tetramer-positive T cells and transferred via a lentiviral vector into TCR-deficient Jurkat 76 cells. Results The crystal structures identified peptide binding to DRB1*04:01 and potential side chain exposure to T cells. The main TCR recognition sites in Col2(259-273) were lysine residues that can be galactosylated. RA T-cell responses to DRB1*04:01-presented Col2(259-273) were dependent on peptide galactosylation at lysine 264. Dynamic molecular modelling of a functionally characterised Col2(259-273)-specific TCR complexed with DRB1*04:01/Col2(259-273) provided evidence for differential allosteric T-cell recognition of glycosylated lysine 264. Conclusions The MHC-peptide-TCR interactions elucidated in our study provide new molecular insights into recognition of a post-translationally modified RA T-cell determinant with a known dominant role in arthritogenic and tolerogenic responses in murine Col2-induced ar

Die Rheumatoide Arthritis (RA) ist eine multifaktoriell bedingte Autoimmunerkrankung, die durch entzündlichen Gelenksbefall charakterisiert ist. Unter fehlender oder ungenügender therapeutischer Intervention nimmt die Erkrankung einen progressiven Verlauf, der zu Gelenkdestruktionen und damit zu zunehmender Behinderung, sowie Arbeitsunfähigkeit führt. Neben den Einschränkungen in der Gelenkfunktion können in jedem Krankheitsstadium Allgemeinsymptome und vielfältige extraartikuläre Manifestationen auftreten, sodass die Erkrankung mit einer verkürzten Lebenserwartung bzw. erhöhter Mortalität assoziiert ist. Obwohl in den letzten Jahren deutliche Fortschritte in der Therapie erzielt wurden, ist eine definitive Heilung nicht möglich. Gemäß der EULAR-Guidelines von 2019 ist Methotrexat (MTX) weiterhin als „anchor drug“ in der RA das Erstlinienmedikament der Wahl. Bei Therapieversagen von MTX und dem Fehlen von negativen Prognoseparametern kann als Zweitlinientherapie ein anderes konventionelles DMARD (csDMARD) in Monotherapie oder Kombination eingesetzt werden. Eine der Optionen ist Leflunomid (LEF), das in Studien seine Wirksamkeit als DMARD und seine Überlegenheit gegenüber Placebo bewiesen hat. Es ist aber nach wie vor nicht wirklich geklärt, ob Patienten im klinischen Alltag tatsächlich von einer Therapie mit LEF oder LEF/MTX profitieren, insbesondere nach dem Versagen einer Erstlinientherapie mit MTX. Dazu wurde in der vorliegenden Untersuchung der Alltagseinsatz und Nutzen von LEF sowohl in Monotherapie als auch in Kombination mit MTX analysiert. Es handelt sich um eine historisch prospektive Kohortenstudie mit Patienten der Rheumatologischen Ambulanz des Universitätsklinikums Dresden. Es erfolgte die Einteilung der Studienkohorte (n=158) in zwei Untergruppen. In der erweiterten LEF-Kohorte (eLEF) befanden sich alle Patienten, welche zu einem beliebigen Zeitpunkt zwischen 2007 und 2015 mit LEF (n=103) oder mit LEF/MTX (n=49) behandelt worden waren. In der post MTX, Rheumatoid arthritis (RA) is a multifactorial autoimmune disease characterized by inflammatory joint involvement. In the absence or inadequacy of therapeutic intervention, the disease takes a progressive course, leading to joint destruction, increasing disability, and incapacity to work. In addition to limitations in joint function, general symptoms and multiple extra-articular manifestations may occur at any stage of the disease, so that the disease is associated with a shortened life expectancy and increased mortality. Although significant advances in therapy have been made in recent years, a definitive cure is not possible. According to the 2019 EULAR guidelines, Methotrexate (MTX) remains the first-line drug of choice as the 'anchor drug' in RA. In case of treatment failure of MTX and the absence of poor prognostic factors, another conventional DMARD (csDMARD) can be used as second-line therapy in monotherapy or combination. One of the options is Leflunomide (LEF), which has demonstrated its efficacy as a DMARD and its superiority to placebo in trials. However, it is still not really clear whether patients actually benefit from therapy with LEF or LEF/MTX in daily clinical practice, especially after failure of first-line therapy with MTX. To this end, the present study analyzed the everyday use and benefit of LEF both in monotherapy and in combination with MTX. It is a historical prospective cohort study with patients of the Rheumatologic Outpatient Clinic of the University Hospital of Dresden. The study cohort (n=158) was divided into two subgroups. The extended LEF cohort (eLEF) included all patients who had been treated with LEF (n=103) or with LEF/MTX (n=49) at any time between 2007 and 2015. The post MTX cohort (pMTX group) included all patients who had been treated with LEF (n=39) or LEF/MTX (n=16) as second-line therapy after failure of first-line MTX between 2007 and 2015. Treatment survival was assessed using Kaplan-Meier curves, and clinical outcome in