Background Autoantibody production is a hallmark of rheumatoid arthritis (RA). Anti-citrullinated protein antibodies (ACPA) are highly disease-specific, and their presence is associated with more... Show moreBackground Autoantibody production is a hallmark of rheumatoid arthritis (RA). Anti-citrullinated protein antibodies (ACPA) are highly disease-specific, and their presence is associated with more severe disease and poor prognosis compared to ACPA-negative patients. However, the immune cell composition associated with antibody-positive/negative disease is incompletely defined. Mass cytometry (MC) is a high-dimensional technique offering new possibilities in the determination of the immune cell composition in rheumatic diseases. Here, we set up a broad phenotyping panel to study the immune cell profile of early untreated RA to investigate if specific immune cell subsets are associated with ACPA+ versus ACPA- RA. Methods Freshly obtained PBMCs of early, untreated RA patients (8 ACPA+ and 7 ACPA-) were analysed using a 36-marker MC panel, including markers related to various immune lineages. Data were processed using Cytosplore for dimensional reduction (HSNE) and clustering. Groups were compared using Cytofast. A second validation cohort of cryopreserved PBMCs obtained from early RA patients (27 ACPA+ and 20 ACPA-) was used to confirm MC data by flow cytometry (FC). FC data were processed and analysed using both an unsupervised analysis pipeline and through manual gating. Results MC indicated no differences when comparing major immune lineages (i.e. monocytes, T and B cells), but highlighted two innate subsets: CD62L(+) basophils (p = 0.33) and a subset of CD16(-) NK cells (p = 0.063). Although the NK cell subset did not replicate by FC, FC replication confirmed the difference in CD62L(+) basophil frequency when comparing ACPA+ to ACPA- patients (mean 0.32% vs. 0.13%; p = 0.01). Conclusions Although no differences in major lineages were found between early ACPA+ and ACPA- RA, this study identified the reduced presence of activated basophils in ACPA-negative disease as compared to ACPA-positive disease and thereby provides the first evidence for a connection between activated basophils and ACPA status. Show less
The objective of this PhD thesis is to understand mast cell (and basophil) functions and their role in autoimmune disease by focusing on three main aims: 1. To characterize the interaction between... Show moreThe objective of this PhD thesis is to understand mast cell (and basophil) functions and their role in autoimmune disease by focusing on three main aims: 1. To characterize the interaction between innate and Fc receptor triggers on mast cell and basophil function 2. To analyze the interaction between mast cells and CD4+ T cells 3. To understand the function of mast cells in chronic inflammation In this thesis I showed that mast cells can significantly contribute to chronic inflammation through their activation by Fc receptors and TLRs, as well as their interaction with CD4+ T cells, thereby increasing our understanding of their role in allergy and autoimmunity and providing several therapeutic targets to prevent mast cell-mediated immune responses. Show less
