mber of IgM and IgG together with autoreactive IgM and IgG anti-dsDNA antibody secreting-cells in the bone marrow and spleen after one-week of treatment in ratio to mean of control, as enumerated by ELISPOT. Values are meanSEM; ns, non-significant, P>0.05, P<0.05; P<0.01, P<0.001, by post-hoc test. Abbreviations: Bz, bortezomib; CD20, anti-mouse CD20 antibody; Int, integrin-blocking antibodies; anti-LFA1 and anti-VLA4 antibodies. doi:10.1371/journal.pone.0135081.g002 plasma cells in the bone marrow, but induced a significant reduction of both IgM and IgG antidsDNA-secreting plasma cells in the spleen. In summary, the fact that BCD did not deplete ASCs or antidsDNA-ASCs in the bone marrow confirms that BCD has limited direct effects on bone marrow LLPCs. Anti-CD20 and integrin blocking were only effective in the spleen, where higher numbers of SLPCs are located. This suggests that autoreactive plasma cells in the bone marrow can only be targeted by the proteasome inhibitor bortezomib. Impact of different short-term depletive therapies on bone marrow and splenic B cells In order to further characterize the effects of the treatments on the B-cell populations and their possible role in blocking the pathogenic regeneration plasmablasts/SLPCs and LLPCs, we enumerated different B-cell subsets in bone marrow and spleen by flow cytometry after treatment. Total PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19723728 CD19+ B cells in the bone marrow and spleen were SB-366791 site depleted significantly by all treatments; anti-CD20 plus bortezomib achieved the strongest effect. Anti-CD20 PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/1972496 alone did not significantly affect early-stage B cells in the bone marrow, but depleted immature and mature B cells significantly. Anti-CD20 plus anti-LFA1/ anti-VLA4 achieved similar results. In contrast, the bortezomib-based treatments substantially 
reduced pro-B cells and significantly decreased pre-, immature and mature B cells. In the spleen, all treatments significantly reduced the number of follicular B cells, but anti-CD20 plus antiLFA1/anti-VLA4 and anti-CD20 plus anti-LFA1/anti-VLA4/Bz achieved the greatest 7 / 17 Long-Term Plasma Cell Depletion Ameliorates SLE Fig 3. Effects of short-term depletion treatments on the numbers of different B-cell subsets in bone marrow and spleen. Percentage of remaining B cell subsets in the bone marrow and spleen in ratio to the mean of control. Bone marrow B-cell subsets identified by flow cytometry: total B cells , bone marrow pro-B cells, pre-B cells, immature B cells, and mature B cells. Splenic B-cell subsets identified by flow cytometry: follicular B cells, marginal zone B cells, germinal center B cells, and B1 B cells. Values are meanSEM; ns, non-significant, P>0.05, P<0.05; P<0.01, P<0.001, post-hoc test. Abbreviations: Bz, bortezomib; CD20, antimouse CD20 antibody; Int, Integrin blocking antibodies; anti-LFA1 and anti-VLA4 antibodies.Long-Term Plasma Cell Depletion Ameliorates SLE reductions. Germinal center B cells were significantly decreased by anti-CD20 plus bortezomib and anti-CD20 plus anti-LFA1/anti-VLA4/Bz. Marginal zone B cells and B1 B cells were resistant to all treatments. MZ and B1 B cell numbers were actually higher in the groups treated with anti-LFA1/anti-VLA4 antibodies. These data show that anti-CD20 antibody can deplete immature and mature B cells in the spleen and bone marrow without affecting early-stage, MZ and B1 B cells. The addition of antiLFA1/anti-VLA4 antibodies to the regimen did not increase the BCD effect, but increased the number of MZ and B1 B cells.