QUANTIFICATION OF CD27+MEMORY B-CELLS IN RHEUMATOID ARTHRITISPATIENTS TREATED WITH RITUXIMAB

Background: Rituximab (RTX) is being increasingly used in treatment of several autoimmune diseases, including Rheumatoid Arthritis (RA).RTX induces a deep depletion of all peripheral B-Cell subsets (memory and naive B-cells). During the B-Cell repopulation phase, occurring approximately after 3 months of RTX administration, B-precursors and naive cells reappear.Several studies have shown that relapsing RA patients are characterized by a relative expansion of memory B cells during the B-Cell repopulation phase Objectives: The aim of this study was to quantify the memory B-Cell compartment in RA patients with different disease activity scores, evaluated by DAS28, during RTX treatment Methods: 26 RA patients under RTX treatment were studied. At the end of th treatment 8/26 showed high-to-moderate activity risk (median DAS28=4.8) and 18 low activity risk or remission (median DAS28=2.69). After a median of 3 months from last RTX infusion, B-Cell subsets (precursors, naive, memory B cells and plasma cells) were quantified in peripheral blood by flow cytometry, using a panel of 8 markers (CD3, CD4, CD8, CD19, CD20, CD27, CD38 and CD45). B naive cells were identified as CD19+ CD20+ CD27-, B memory cells were identified as CD19+ CD20+ CD27+, plasma cells as CD19+ CD38++ CD27++ CD20- and B precursors as CD19+ CD38++ CD20- CD27-, respectively. Percent and absolute values were calculated for each subset. In adition 10 healthy subjects were included as negative control group (NC). Results: The median percent and absolute values of B naive cells, B memory cells and plasma cells identified in NC, non-responder RA patients with high/moderate disease activity and responder RA patients with low disease activity or in remission are reported in Table 1. The virtual absence of peripheral B-Cell was defined as Conclusion: We used a sensitive and easily applicable flow cytometric multicolor panel that allowed the accurate and standardized identification and enumeration of peripheral blood B-Cell subsets. As reported by other studies, higher levels of memory B-Cells were found in non responder RA patients treated by RTX, approaching those of healthy individuals. References [1] Lopez J. Clin Exp Rheumatol2018; Dec 19. Sellam J. Arthritis Rheum 2011; 63: 3692-3701.Dass S. Arthritis Rheum2008; 58: 2993-2999 Disclosure of Interests: None declared