Characterisation of age-associated B cells in rheumatoid arthritis patients

Ph. D. ThesisRheumatoid arthritis (RA) is a chronic autoimmune disorder characterised by joint inflammation and bone destruction. The presence of autoantibodies, years before the clinical onset of disease, and the efficacy of rituximab, a B-cell depleting therapy, highlight a pathogenic role for B cells in the initiation and development of RA. Different groups have recently identified a novel subset of B cells named age-associated B cells (ABCs). Studies in murine autoimmune models and patients suffering from autoimmune diseases described these cells as CD19high CD21- CD11c+. Moreover, a subset of synovial fluid B cells with a similar phenotype, also expressing FcRL4, has been demonstrated to contribute to RA pathogenesis. I aimed to fully characterise, phenotypically, transcriptionally and functionally, peripheral blood ABCs in patients suffering from early RA. I have shown that although my study did not show significant differences in the frequency of peripheral blood ABCs between RA patients and other disease and healthy controls, the percentage of cells with an ABC phenotype in the synovial fluid is very high in patients suffering from inflammatory arthritides. I characterised these cells phenotypically and confirmed that they have high expression of activation and co-stimulatory molecules, in addition to expressing high levels of T-bet and the members of the FcRL family (i.e. FcRL2-5). Moreover, these cells are actively proliferating and a high proportion of them have a class-switched memory B cells phenotype expressing IgG. Interestingly, the transcriptome analysis showed that the ABCs are a subset of B cells, distinct from naïve, CD5+ and memory B cell subsets, with a unique transcriptome profile. ABCs had a high expression of chemokine receptors, such as CXCR3, as well as adhesion molecules, such as integrins and CD97, supporting a role for the migration of these cells into inflammatory sites. In addition, ABCs also had high expression of apoptotic markers, such as caspases and Fas. Finally, the functional characterisation of ABCs showed that these cells are capable of secreting IgM and IgG after stimulation. However, due to low cell numbers and high cell death, very low quantities of secreted cytokines were detected; making it very difficult to determine if these cells could contribute to inflammation. Overall, I confirmed that the ABC subset is an activated memory-like B cell subset which could potentially migrate into inflammatory sites and promote disease pathogenesis. However, exactly how these cells contribute to RA pathogenesis is still unknown and further functional work will help elucidate their role in autoimmunity.Versus Arthriti

Famílies botàniques de plantes medicinals

Facultat de Farmàcia, Universitat de Barcelona. Ensenyament: Grau de Farmàcia, Assignatura: Botànica Farmacèutica, Curs: 2013-2014, Coordinadors: Joan Simon, Cèsar Blanché i Maria Bosch.Els materials que aquí es presenten són els recull de 175 treballs d’una família botànica d’interès medicinal realitzats de manera individual. Els treballs han estat realitzat per la totalitat dels estudiants dels grups M-2 i M-3 de l’assignatura Botànica Farmacèutica durant els mesos d’abril i maig del curs 2013-14. Tots els treballs s’han dut a terme a través de la plataforma de GoogleDocs i han estat tutoritzats pel professor de l’assignatura i revisats i finalment co-avaluats entre els propis estudiants. L’objectiu principal de l’activitat ha estat fomentar l’aprenentatge autònom i col·laboratiu en Botànica farmacèutica

Upregulation of FcRL4 expression on age related B cells (ABC) allows capture of IgA immune complexes

Introduction: FcRL4 is an inhibitory receptor which is mainly expressed by B cells localised in the mucosa associated lymphoid tissue and at sites of chronic inflammation. FcRL4 can act as a low affinity IgA receptor, and FcRL4+ B cells from sites of inflammation carry captured IgA aggregates on their surface. FcRL4 expression, at a low level, can also be detected on peripheral blood (PB) CD21low/CD11c+ age related B cells (ABC). We addressed the question whether the level of FcRL4 expression on ABC ex vivo or after stimulation allows them to capture IgA aggregates on their surface. Methods: FcRL4 expression and IgA binding were analysed by flow cytometry in B cell populations from synovial fluid (SF), peripheral blood (PB), and tonsils, as well as TLR-7 and TLR-9β agonists and TGF-β stimulated PB B cells. PBMCs were treated with 0.1M glycine buffer (pH3) and human colostrum IgA to remove or add IgA to the B cell surface. Results: The CD21loCD11chi phenotype and FcRL4 expression coincide in PBMC and SF B cells but only in a small proportion of tonsil B cells. While SF and tonsil FcRL4+ B cells carry IgA aggregates on their surface this was not detectable in PB B cells. In vitro stimulated CD21loCD11chi B cells significantly increased their FcRL4 expression and were able to capture IgA aggregates on their surface. Conclusions: While circulating ABC express low but detectable levels of FcRL4, this is not sufficient to capture IgA aggregates. Upregulation of FcRL4 on CD21loCD11chi ABCs can allow them to capture IgAIC indicating that there is a threshold level of FcRL4 expression that is required to bind IgAIC and that additional stimulatory signals can enable IgA capture in ABC.<br/