CXCR5, BAFF-R, BCMA, and TACI expression in BM and PB B cells of patients with ITP and HCs. (A) Representative density plots of CXCR5 on CD19⁺ cells in BM and PB of patients with ITP and HCs. (B, C) BM (69.25 ± 4.27% vs 26.28 ± 2.64%; P < .001) and PB (median [range], 90.78% [80.86%-96.06%] vs 85.13% [56.76%-91.61%]; P = .046) B cells from patients with ITP had elevated levels of CXCR5 compared with those from HCs. (D, E) Surface CXCR5 level on B cells in PB was significantly higher than in BM, both from patients with ITP (median [range], 72.36% [57.54%-92.65%] vs 90.37% [59.93%-96.06%]; P = .006) and HCs (30.12 ± 3.82% vs 76.86 ± 4.86%; P = .003). (F) Representative density plots of BAFF-R on CD19⁺ cells in the BM and PB of patients with ITP and HCs. (G, H) BM and PB B cells from patients with ITP had elevated levels of BAFF-R compared with HCs (BM: median [range], 84.10% [60.30%-97.54%] vs 37.08% [16.56%-52.58%], P < .001; PB: median [range], 93.97% [87.20%-97.76%] vs 90.97% [76.97%-95.09%], P = .016). (I, J) BAFF-R expression on B cells was remarkably higher in PB than in BM, both from patients with ITP and from HCs (patients with ITP: median [range], 85.75% [60.30%-97.54%] vs 93.83% [87.20%-97.38%], P = .002; HCs: median [range], 37.76% [16.56%-58.27%] vs 89.00% [76.97%-95.09%], P = .031). (K) Representative density plots of BCMA on CD19⁺ cells in BM and PB of patients with ITP and HCs. (L, M) BM B cells from patients with ITP exhibited elevated BCMA levels compared with HCs (median [range], 6.04% [0.77%-22.76%] vs 3.77% [1.24%-6.55%]; P = .018), whereas there was no statistical difference in PB B-cell BCMA levels between patients with ITP and HCs. (N, O) No statistical difference was found in B-cell BCMA levels between BM and PB in patients with ITP (P = 0.454), whereas the level of B-cell BCMA in PB was considerably higher than in BM in HCs (2.91 ± 0.52% vs 4.47 ± 0.67%; P = .009). (P-S) No statistical difference was found in BM or PB B-cell TACI levels between patients with ITP and HCs. Furthermore, no statistical difference in B-cell TACI level between BM and PB was observed in patients with ITP or in HCs (all P > .05). *P < .05; **P < .01; ***P < .001. PE, phycoerythrin; SSC, side scatter.