Persistent depletion of long-lived plasma cells (LLPCs) using cyclophosphamide in combination with bortezomib. Twelve- to 16-wk-old NZB/W F1 mice were treated with: (1) one bortezomib cycle (black dots and black line); (2) intraperitoneal injection of 35 mg/kg bw cyclophosphamide on day 0, 3, 7 and (open dots, dotted line); (3) one bortezomib cycle combined with cyclophosphamide on day 0, 3, 7 and 11 (gray dots, connecting line). (A) Absolute numbers of short-lived MHChigh in the spleen and long-lived MHC-IIlow plasma cells in the spleen (left) and bone marrow (right) 12 h and 3, 7, and 15 days after the last bortezomib injection measured by flow cytometry. (B) Frequencies of the remaining anti-double-stranded DNA (anti-dsDNA)-secreting cells in the spleen (left) and bone marrow (right) calculated by comparison with untreated mice (day 0), as detected by enzyme-linked immunospot (ELISPOT) 15 days after the last bortezomib injection. n = 4 mice treated with bortezomib, n = 3 with cyclophosphamide and n = 4 with bortezomib plus cyclophosphamide. Data represent mean and standard error of the mean (SEM). Numbers and horizontal bars represent P values from statistical comparison between groups at the end of the observation period (15 days after the bortezomib cycle). n.s., nonsignificant. P >0.05, *
P ≤0.05, **
P ≤0.01 by two-tailed unpaired t test.