High levels of B-cell activating factor in patients with active chronic graft-versus-host disease

Abstract

Purpose: Recent studies suggest that donor B cells as well as T cells contribute to immune pathology in patients with chronic graft-versus-host disease (GVHD). B-cell activating factor (BAFF) promotes survival and differentiation of activated B cells. Thus, we tested whether BAFF correlated with chronic GVHD disease activity and time of onset after allogeneic hematopoietic stem cell transplantation (HSCT).

Experimental design: Patients who had undergone allogeneic HSCT between 1994 and 2005 for hematologic malignancies were studied. ELISA was used to measure plasma BAFF levels and flow cytometry was used to assess BAFF receptor expression on B cells in patients with or without chronic GVHD.

Results: In 104 patients, BAFF levels were significantly higher in patients with active chronic GVHD compared with those without disease (P = 0.02 and 0.0004, respectively). Treatment with high-dose prednisone (>or=30 mg/d) was associated with reduced BAFF levels in patients with active chronic GVHD (P = 0.0005). Serial studies in 24 patients showed that BAFF levels were high in the first 3 months after HSCT but subsequently decreased in 13 patients who never developed chronic GVHD. In contrast, BAFF levels remained elevated in 11 patients who developed chronic GVHD. Six-month BAFF levels >or=10 ng/mL were strongly associated with subsequent development of chronic GVHD (P < 0.0001). Following transplant, plasma BAFF levels correlated inversely with BAFF receptor expression on B cells (P = 0.01), suggesting that soluble BAFF affected B cells through this receptor.

Conclusion: These results suggest that elevated BAFF levels contribute to B-cell activation in patients with active chronic GVHD.

Fig. 1

Plasma BAFF levels in patients with chronic GVHD. A, BAFF levels measured by ELISA in 104 patients with and without chronic GVHD after allogeneic HSCT and in healthy donors. The patients with chronic GVHD were further categorized into limited or extensive disease groups according to the Seattle criteria (12). Lines within box plots, median value for each group; bottom and top whiskers, 25th and 75th percentiles, respectively; black squares, outliers. B, effect of high-dose prednisone on plasma BAFF levels. BAFF levels in the same cohort of 104 patients with extensive, limited, or inactive chronic GVHD after allogeneic HSCT, separated into groups of patients receiving ≥30 mg/d prednisone versus patients receiving <30 mg/d prednisone. C, serial plasma BAFF measurements of samples from 13 patients who never developed chronic GVHD and from 11 patients who developed chronic GVHD between 7 and 12 mo after HSCT.

Fig. 2

Comparison of soluble BAFF to total CD19⁺ B-cell number in peripheral blood after allogeneic HSCT. Solid line, no/inactive chronic GVHD; dashed line, active chronic GVHD; circles, patients with no/inactive chronic GVHD; triangles, patients with active chronic GVHD at the time of sample collection.

Fig. 3

Expression of BAFF-R on the surface of CD19⁺ B cells after allogeneic HSCT. Monoclonal anti-human BAFF-R (BR3 FITC) and anti-human CD19⁺PC7 were used to detect cell surface BAFF-R expression on B cells in whole blood samples (see Materials and Methods). A, representative flow cytometry dot blot analyses of CD19⁺ and BAFF-R expression are shown for representative samples from a healthy donor, a patient without chronic GVHD (cGVHD), a patient with an inactive chronic GVHD, and a patient with active chronic GVHD. B, whisker plot showing median percentage of CD19⁺ B cells that coexpress BAFF-R in a healthy donors, patients with inactive/no chronic GVHD, and patients with active chronic GVHD. Lines within box plots, median value for each group; bottom and top whiskers, 25th and 75th percentiles, respectively; black squares, outliers. C, soluble BAFF levels in plasma are compared with the percentage of CD19⁺ B cells expressing cell surface BAFF-R in 43 patient samples after HSCT. Solid heavy line, smoothing spline curve fit for extensive/limited values; circles, patients with no/inactive chronic GVHD; triangles, patients with extensive/limited chronic GVHD at the time of sample collection.