Background/Purpose: Background: B-cell depletion with rituximab (RTX) is an effective treatment for ANCA-associated vasculitis (AAV) patients. Repeated RTX upon B-cell repopulation or return of ANCAs improved therapeutic efficacy, which indicates the presence of minimal residual autoimmunity (MRA) after RTX. Therefore, this study aimed to perform in-depth phenotypic and functional analyses of B and plasma cells after RTX in AAV.

Methods: Methods: EuroFlow-based highly sensitive flow cytometry (HSFC) was used during longitudinal follow-up of RTX-treated AAV patients (n=12). To investigate MRA in the memory B-cell compartment after RTX, peripheral blood mononuclear cells (PBMCs) were stimulated with CpG, IL-2 and IL-21 in vitro to induce plasma cells (PCs) and ANCA-IgG and -IgM were measured in these supernatants and in paired serum samples by ELISA.

Results: Results: By employing HSFC we demonstrated that 12 weeks after RTX, low but significant numbers of circulating CD19⁺ B cells (0.21^*10⁶ cells/L) could still be detected (reduction of -99.7%). While naïve B-cells, memory B-cells and CD20⁺ plasmablasts (PB) were rapidly depleted, CD20^– PCs were reduced slower and depleted incompletely. Residual CD20^– PCs were 0.05^*10⁶ cells/L (-95.8% from baseline), whereof 57% were mature CD138⁺ PCs. Early repopulation at 12 weeks was dominated by CD20^–CD138^– PCs, followed by CD20⁺ PBs at 24 weeks while memory and naïve B cells remained suppressed. Simultaneously, serum ANCA IgG, IgM and IgA, produced by autoreactive PCs, decreased but did not disappear after RTX. Interestingly, 24 weeks after RTX, serum anti-MPO IgM increased in 3/4 patients, which associated with repopulating CD20⁺ PBs. This suggested remaining autoreactive B cells despite RTX treatment, which was further studied by in vitro PBMC cultures. In these supernatants both anti-MPO-IgG and -IgM were detected at baseline, whereas anti-MPO IgG disappeared after RTX, in contrast to anti-MPO IgM, which was detected 24 weeks after RTX.

Conclusion: Conclusion: RTX results in a strong but not complete B cell depletion. In-depth analysis demonstrated that both ANCA-producing PCs and ANCA-memory B cells can be detected after RTX, indicating residual B-cell autoimmunity in AAV patients. Further identification of MRA could be worthwhile for guiding personalized treatment in AAV patients.

« Back to 2019 ACR/ARP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/minimal-residual-autoimmunity-after-rituximab-in-anca-associated-vasculitis-patients/