Abatacept modulates CD80 and CD86 expression and memory formation in human B-cells

Background: Cytotoxic T lymphocyte antigen-4 (CTLA-4) limits T-cell activation and is expressed on T-regulatory cells. Human CTLA-4 deficiency results in severe immune dysregulation. Abatacept (CTLA-4 Ig) is approved for the treatment of rheumatoid arthritis (RA) and its mechanism of action is attributed to effects on T-cells. It is known that CTLA-4 modulates the expression of its ligands CD80 and CD86 on antigen presenting cells (APC) by transendocytosis. As B-cells express CD80/CD86 and function as APC, we hypothesize that B-cells are a direct target of abatacept. Objectives: To investigate direct effects of abatacept on human B-lymphocytes in vitro and in RA patients. Methods: The effect of abatacept on healthy donor B-cells’ phenotype, activation and CD80/CD86 expression was studied in vitro. Nine abatacept-treated RA patients were studied. Seven of these were followed up to 24 months, and two up to 12 months only and treatment response, immunoglobulins, ACPA, RF concentrations, B-cell phenotype and ACPA-specific switched memory B-cell frequency were assessed. Results: B-cell development was unaffected by abatacept. Abatacept treatment resulted in a dose-dependent decrease of CD80/CD86 expression on B-cells in vitro, which was due to dynamin-dependent internalization. RA patients treated with abatacept showed a progressive decrease in plasmablasts and serum IgG. While ACPA-titers only moderately declined, the frequency of ACPA-specific switched memory B-cells significantly decreased. Conclusions: Abatacept directly targets B-cells by reducing CD80/CD86 expression. Impairment of antigen presentation and T-cell activation may result in altered B-cell selection, providing a new therapeutic mechanism and a base for abatacept use in B-cell mediated autoimmunity.Fil: Lorenzetti, Raquel. Albert Ludwigs University of Freiburg; AlemaniaFil: Janowska, Iga. Albert Ludwigs University of Freiburg; AlemaniaFil: Smulski, Cristian Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Frede, Natalie. Albert Ludwigs University of Freiburg; AlemaniaFil: Henneberger, Nadine. Albert Ludwigs University of Freiburg; AlemaniaFil: Walter, Lea. Albert Ludwigs University of Freiburg; AlemaniaFil: Schleyer, Marei-Theresa. Albert Ludwigs University of Freiburg; AlemaniaFil: Hüppe, Janika M.. Albert Ludwigs University of Freiburg; AlemaniaFil: Staniek, Julian. Albert Ludwigs University of Freiburg; AlemaniaFil: Salzer, Ulrich. Albert Ludwigs University of Freiburg; AlemaniaFil: Venhoff, Ana. Albert Ludwigs University of Freiburg; AlemaniaFil: Troilo, Arianna. Albert Ludwigs University of Freiburg; AlemaniaFil: Voll, Reinhard Edmund. Albert Ludwigs University of Freiburg; AlemaniaFil: Venhoff, Nils. Albert Ludwigs University of Freiburg; AlemaniaFil: Thiel, Jens. Albert Ludwigs University of Freiburg; AlemaniaFil: Rizzi, Marta. Albert Ludwigs University of Freiburg; Alemani

JAK inhibitors differentially modulate B cell activation, maturation and function: A comparative analysis of five JAK inhibitors in an in-vitro B cell differentiation model and in patients with rheumatoid arthritis

BackgroundJanus kinase (JAK) inhibitors have been approved for the treatment of several immune-mediated diseases (IMIDs) including rheumatoid arthritis (RA) and psoriatic arthritis and are in clinical trials for numerous other IMIDs. However, detailed studies investigating the effects of different JAK inhibitors on B cells are missing. Within this study, we therefore aimed to characterize the effect of JAK inhibition on the B cell compartment.MethodsTo this end, we investigated the B cell compartment under JAK inhibition and compared the specific effects of the different JAK inhibitors tofacitinib (pan-JAK), baricitinib (JAK1/2), ruxolitinib (JAK1/2), upadacitinib (JAK1/2) as well as filgotinib (selective JAK1) on in-vitro B cell activation, proliferation, and class switch recombination and involved pathways.ResultsWhile B cell phenotyping of RA patients showed an increase in marginal zone (MZ) B cells under JAK inhibition, comparison with healthy donors revealed that the relative frequency of MZ B cells was still lower compared to healthy controls. In an in-vitro model of T-cell-independent B cell activation we observed that JAK1/2 and selective JAK1 inhibitor treatment led to a dose-dependent decrease of total B cell numbers. We detected an altered B cell differentiation with a significant increase in MZ-like B cells and an increase in plasmablast differentiation in the first days of culture, most pronounced with the pan-JAK inhibitor tofacitinib, although there was no increase in immunoglobulin secretion in-vitro. Notably, we further observed a profound reduction of switched memory B cell formation, especially with JAK1/2 inhibition. JAK inhibitor treatment led to a dose-dependent reduction of STAT3 expression and phosphorylation as well as STAT3 target gene expression and modulated the secretion of pro- and anti-inflammatory cytokines by B cells.ConclusionJAK inhibition has a major effect on B cell activation and differentiation, with differential outcomes between JAK inhibitors hinting towards distinct and unique effects on B cell homeostasis