Session Type: Abstract Submissions (ACR)
The B cell-associated receptor, CD22, functions to regulate adhesion and signaling through both the B cell receptor (BCR) and Toll-like receptors (TLRs) expressed in B cells. Epratuzumab is a humanized monoclonal antibody that targets CD22 on B cells and is currently being tested in phase 3 clinical trials in patients with systemic lupus erythematosus (SLE). This study was undertaken to determine how epratuzumab affects B cell activation through TLR and/or BCR pathways in tonsil-derived B cell subsets, which offers the opportunity to investigate the responses of B cells from human lymphoid tissue.
Purified CD19+CD20+ B cell subsets were isolated from human tonsils based on their relative expression of CD10, CD27 and other markers, and examined for CD22 expression and internalization after binding of epratuzumab using conventional flow cytometry and ImageStream® multispectral imaging cytometry. Isolated subsets were also treated with anti-IgM, R848 (a TLR7 agonist) and/or interferon (IFN)-α in the presence of epratuzumab or a human IgG1 control. Changes in mRNA levels of a variety of genes 3 to 12 hours after activation were analyzed by qPCR. Cell proliferation was assessed by flow cytometry using CFSE staining. Cytokine production was measured by ELISA and intracellular flow cytometry after 3 days of in vitro culture.
CD22 was expressed on all B cell subsets but CD20+CD10loCD27lo mature naïve B cells expressed higher levels of CD22 (MFI 148) than CD20+CD27hiCD10lo memory B cells (MFI 120) or CD10hiCD27+ germinal center (GC)-associated B cells (MFI 130), and naïve B cells also internalized epratuzumab more uniformly compared to GC-associated B cells. Epratuzumab had no effect on IFN-α induced genes (eg. TLR7, IRF7) or BCR-induced genes (eg. c-MYC) in naïve B cells. However, epratuzumab did affect the expression of certain cytokine genes after TLR7 stimulation alone and/or in combination with anti-IgM (eg. IL-6). TLR7-driven IL-6 and IL-10 expression by naïve B cells were also differentially modulated by epratuzumab, with inhibition of IL-6 cytokine production but enhanced IL-10 expression. Finally, epratuzumab demonstrated a small but consistent enhancement of B cell proliferation induced with anti-IgM and anti-IgM+ R848.
These results suggest that one therapeutic effect of epratuzumab may be via down-regulation of the production of pro-inflammatory cytokines by B cells and an increase in the production of regulatory cytokines such as IL-10. These data have implications for understanding the functional consequences on B cell function of epratuzumab treatment in patients with autoimmune diseases such as SLE.
N. V. Giltiay,
G. L. Shu,
E. A. Clark,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/regulation-of-the-responses-of-human-b-cell-subsets-to-innate-immune-signals-by-epratuzumab-a-humanized-monoclonal-antibody-targeting-cd22/