Background/Purpose: The immune system is a complex network of cells preventing the invasion of the organism from external particles. The break in the homeostasis will lead to the development of diseases including autoimmune diseases such as systemic lupus erythematosus. Among controlling cells, dysfunctional regulatory B cells (Breg) were pointed out, as they were unable to modulate inflammatory T cell activity. In parallel, our laboratory described that the presence of an abnormal glycosylation of B cell subpopulations as well as serum proteins and immunoglobulin in those lupus patients. In fact, these B cells, through lectin flow cytometry, shown important decrease in N-linked glycosylation and lack of fucose residues. Glycosylation was largely described as being part of various several physiological process including cell differentiation. This is the reason why we decided to investigate whether those anomalies could be responsible for Breg deficiencies.

Methods: An in vitro model of Breg differentiation was set up. It consists in prestimulating B cells with CpG (a TLR-9 ligand) and multimerized CD40L for 3 days followed with a 4.5 days of coculture with CFSE-labelled T cells with a 1:1 ratio. B cell glycosylation was evaluated by using biotinylated lectins specific for different sugar patterns typical of O- and N-type glycosylation combined with streptavidin-FITC. Glycosylation profile (at day 0, 3 and 7.5) as well as the proliferation of T cells (at day 7.5) were assessed by flow cytometry.

Results: B cell prestimulation (day 3) was correlated with an increase in all glycosylations including N-, O-type as well as fucosylation (except α1-4 residues) except sialylation patterns that remains unchanged. After the contact with T cells (day 7.5), Breg displayed a significant reduction (closed to the basal level) in N-complex residues only, as well as O-glycosylation and fucosylation epitopes (except α1-4 residues) meanwhile sialylation was strongly up-regulated. Clearly, two specific glycosidic signatures were defined during the acquisition of regulatory functions and their manifestations on T cell proliferation.

Conclusion: The next step of this project is to use several inhibitors of the enzymes involved in the definition of these glycosidic signatures in order to evaluate their impacts on the Breg functions and to try them on cells from lupus patients to determine if we could restore some regulatory properties of their B cells.

Ultimately, the aim of this research is to develop new therapeutic tools focus on the glycosylation modulation targeted to specific cells.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/unlocking-the-secrets-of-breg-dysfunction-in-lupus-glycosylation-patterns-as-therapeutic-targets/