Effect of rituximab treatment on T and B cell subsets in lymph node biopsies of patients with rheumatoid arthritis

OBJECTIVES: The exact underlying mechanism of rituximab treatment in patients with RA is poorly defined and knowledge about the effect of B cell depletion on immune cells in secondary lymphoid organs is lacking. We analysed lymphoid tissue responses to rituximab in RA patients. METHODS: Fourteen RA patients received 2 × 1000 mg rituximab intravenously, and lymph node (LN) biopsies were obtained before and 4 weeks after the first infusion. Tissues were examined by flow cytometry, immunohistochemistry and quantitative PCR. LN biopsies from five healthy individuals (HC) served as controls. RESULTS: LN biopsies of RA patients showed increased frequencies of CD21(+)CD23(+)IgD(high)IgM(variable) follicular B cells and CD3(+)CD25(+)CD69(+) early activated, tissue resident T cells when compared with HCs. After treatment, there was incomplete depletion of LN B cells. There was a significant decrease in CD27(−)IgD(+) naïve B cells, and CD27(+)IgD(+) unswitched memory B cells including the CD27(+)IgD(+)IgM(+) subset and follicular B cells. Strikingly, CD27(+)IgD(−) switched memory B cells persisted in LN biopsies after rituximab treatment. In the T cell compartment, a significant decrease was observed in the frequency of early activated, tissue resident T cells after rituximab treatment, but late activated T cells persisted. B cell proliferation inducing cytokine IL-21 was higher expressed in LN biopsies of RA patients compared with HC and expression was not affected by rituximab treatment. CONCLUSION: Rituximab does not cure RA, possibly due to persistence of switched memory B cells in lymphoid tissues suggesting that factors promoting B cell survival and differentiation need to be additionally targeted.