Decreased CD5⁺ B cells in active ANCA vasculitis and relapse after rituximab

Abstract

Background and objectives: B cell significance in ANCA disease pathogenesis is underscored by the finding that ANCA alone can cause disease in mouse models and by the effectiveness of rituximab as therapy in ANCA-small vessel vasculitis (ANCA-SVV). To avoid infections and adverse events from therapy, clinicians require improved markers of disease activity and impending relapse to guide immunosuppression strategies after rituximab treatment.

Design, setting, participants, & measurements: The B cell phenotype was investigated in patients with active ANCA-SVV and in remission. From 2003 to 2009, 54 patients were followed longitudinally for 4-99 months and compared with 68 healthy controls. In a subset of 19 patients, the B cell immunophenotype was examined in samples after rituximab therapy.

Results: Patients with active ANCA-SVV had lower %CD5(+) B cells, whereas %CD5(+) B cells from patients in remission were indistinguishable from healthy controls. After rituximab, median time to relapse was 31 months in patients maintaining normalized %CD5(+) B cells, with or without maintenance immunosuppression. Among patients whose B cells repopulated with low %CD5(+) B cells or had a sharply declining %CD5(+) B cells, those who were on low or no maintenance immunosuppression relapsed sooner (median 17 months) than patients who were maintained on high levels of oral maintenance immunosuppression (29 months; P=0.002).

Conclusions: The %CD5(+) B cells, as a component of the human B regulatory cell phenotype, is a useful indicator of disease activity, remission, and future relapse, and thus may guide remission maintenance therapy after rituximab treatment.

Figure 1.

The %CD5⁺ B cells decreases in active ANCA disease and rebounds with remission. (A) Shown are the %CD5⁺ B cells in healthy controls (□, n=68), patients with active disease (◊, n=24), and patients in remission (○, n=19). Error bars represent the mean ± SD. The %CD5⁺ B cells is lower in patients with active disease (P<0.001) and returns to levels similar to healthy controls during remission of disease (P=0.81). (B) Paired active and remission samples from eight patients demonstrate the increase in %CD5⁺ B cells observed as an individual transitions from active disease to remission (P=0.01). (C and D) The relationship between %CD5⁺ B cells (●) on the left axis and BVAS (▴) on the right axis over time is depicted; the immunosuppression dose (grams per day) is indicated on the right axis (D). A reciprocal pattern of %CD5⁺ B cells and BVAS is observed in a patient (C) who is active at time 0, enters remission at 3 months as %CD5⁺ B cells reach normal levels, and then relapses at 9 months after a steady decline in %CD5⁺ B cells. A representative example of a patient who maintained a normal %CD5⁺ B cells over 82 months and remained in remission off therapy with a persistently high MPO-ANCA titer during this period is shown in D. HC, healthy controls; Act, active disease; Rem, remission; BVAS, Birmingham Vasculitis Activity Score; MPO, myeloperoxidase (MPO).

Figure 2.

Decrease in %CD5⁺ B cells is associated with an increase in disease activity. Examples of the longitudinal relationship between %CD5⁺ B cells (○) on the left axis compared with BVAS (∆) and CellCept (MMF) dose (□) on the right axis over time before and/or after rituximab are depicted (A– C). (A) Patient 158 (group 2), who had 85% CD5⁺ B cells before full B cell recovery (<1% B cells at 6 m, shadowed circle), showed a precipitous drop in CD5 during the next 3–6 months after B cell recovery. Because this patient appeared to be in clinical remission, the CellCept dose was decreased during this time period and the patient flared 12 months after rituximab treatment. (B) Patient 1551 (group 3) had a BVAS of 12 and 5.6% CD5⁺ B cells before rituximab treatment. Although the %CD5⁺ cells is initially normal at B cell repopulation, it steadily declines over the next 2.5–20 months without overt clinical activity in the context of high immunosuppression until month 27. (C) Another group 3 patient, 539, had a decrease in %CD5⁺ cells from 9 to 23 months after rituximab therapy with “no signs of active disease” at months 18 and 23. Upon self-discontinuation of CellCept while %CD5⁺ B cells were below normal, the patient flared before the clinic visit at 29 months. The %CD5⁺ B cells, BVAS, and CellCept dose during the time period between 23 and 29 months are depicted by dashed lines to indicate inferred information. The %CD5⁺ B cells are assumed to be the same as the previous sample; the BVAS is assumed to be at least equal to the subsequent sample. Asterisks indicate the approximate time of flare gleaned from clinic notes for this time period. BVAS, Birmingham Vasculitis Activity Score; MMF, mycophenolate mofetil.

Figure 3.

The %CD5⁺ B cells reflect putative B regulatory cells. (A) The %CD5⁺ B cells correlates with the percentage of B regulatory cells identified as CD24^hiCD38^hi B cells (R²=0.50). This correlation includes all samples for which both CD19⁺CD5⁺ and CD19⁺CD24^hiCD38^hi data were available (21 healthy controls, 17 with active disease, 13 in remission). (B) The correlation between percentages of CD24^hiCD38^hi (dash-dot line), IgM⁺CD5⁺ (dash-dash line), and CD5⁺ B cells (solid line) are shown for two representative patients for whom all three stain sets were available.