Fig 2: CD138 improves defective activation of CD138- T cells. (A) Bar charts showing serum levels of IFN-γ, IFN-α, TNF, IL-6, IL-10, IL-17, IL-21 and IL-2 in MRL/MPJ and MRL/lpr mice. (B) Flow cytometry analyses and bar chart demonstrating the frequencies of CD69+ cells in CD138- T cells in fresh splenocytes from MRL/MPJ mice aged 17-18 weeks, and in CD138- and CD138+ T cells in fresh splenocytes from MRL/lpr mice aged 17-18 weeks. (C) Flow cytometry analyses and bar chart demonstrating the frequency of CD69+ cells in CD138- T cells in fresh splenocytes from MRL/MPJ mice aged 17-18 weeks, and in CD138- and CD138+ T cells in fresh splenocytes from MRL/lpr mice aged 17-18 weeks after 5 h in vitro PI stimulation. (D) Flow cytometry analyses and bar charts demonstrating CD69+ cell frequencies in CD138- T cells in splenocytes from MRL/lpr mice after 0, 2 and 4 h PI stimulation and FasL expression in CD138- T cells in splenocytes from MRL/lpr mice with or without 4 h PI stimulation. (E) Flow cytometry analyses and bar chart demonstrating FasL expression in CD3+CD138+ and CD3+CD138- T cells from MRL/lpr mouse splenocytes with 4 h PI stimulation in. n=4-8 per group/experiment. *P<0.05 and **P<0.01 by one-way analysis of variance. IFN, interferon; TNF, tumor necrosis factor; IL, interleukin; MRL/MPJ, Murphy Roths Large; MRL/lpr, Murphy Roths Large lymphoproliferative; FasL, Fas ligand; PI, ionomycin; MFI, mean or median fluorescence intensity.

Fig 3: CD138 expression leads to defective apoptosis of T cells. (A) Flow cytometry analyses and bar chart showing the frequencies of CD138+ cells in CD3+ T cells from fresh splenocytes of MRL/MPJ and MRL/lpr mice aged 17-18 weeks. (B) Frozen kidney sections stained with CD3 (red), CD138 (green) and DAPI (blue) demonstrate CD138+ T cell infiltration into the renal tissues of MRL/lpr mice (original magnification, x200). (C) Flow cytometry analyses and bar chart showing the frequency of apoptotic cells in CD3+CD138+ T cells of fresh splenocytes in MRL/MPJ and MRL/lpr mice. (D) Flow cytometry analyses and bar charts demonstrating the frequencies of apoptotic and live cells in CD3+CD138- and CD3+CD138+ T cells in fresh splenocytes of MRL/lpr mice. (E) Flow cytometry analyses and bar charts showing CD69+ and CD25+ cell frequencies and FasL expression in CD3+CD138- and CD3+CD138+ T cells in fresh splenocytes from MRL/lpr mice. (F) Flow cytometry analyses and bar charts demonstrating FasL expression in CD138- and CD138+ DN T cells in fresh splenocytes from MRL/lpr mice. (G) Flow cytometry analyses and bar chart demonstrating CD138+ cell frequencies of DN, CD4+ and CD8+ T cells in fresh splenocytes from MRL/lpr mice, and in fresh splenocytes from MRL/lpr mice that were cultured in vitro for 48 and 72 h with no stimulation. (H) Flow cytometric analyses of CD4 expression in CD4+ T cell subsets. CD4+ T cells of MRL/lpr mice were demonstrated to have two cell subsets, namely CD4 hi and CD4 int T cells. CD4 int T cells had significant downregulation of CD4 expression with simultaneous expression of B220. (I) Bar chart indicating CD4 expression in CD4+CD138+ and CD4+CD138- T cells in MRL/lpr mice. (J) CD4+CD138+ T cells expressed B220 and were in the B220+CD4 int T cell subsets. n=4-6 per group/experiment. **P<0.01 by one-way analysis of variance. MRL/MPJ, Murphy Roths Large; MRL/lpr, Murphy Roths Large lymphoproliferative; FasL, Fas ligand; DN, double negative; 7-AAD, 7-aminoactinomycin D; MFI, mean or median fluorescence intensity.

Fig 4: In vitro experiments to verify the biological functions of map‐PD‐L1. Spleen lymphocytes were cocultured with rgEC. For the T cell activation assay, cells were cocultured with anti‐CD3 and anti‐CD28 antibodies for 1 day as a stimulation protocol. In the experimental group, map‐PD‐L1 was anchored to rgEC. Apoptosis (a) and activation (b) of T cells were analyzed by PI and annexin V staining, and CD69 molecular markers, respectively. (c) Detection of rgEC apoptosis after coculture with spleen lymphocytes using a TUNEL Apoptosis Assay Kit. Original magnification, ×400. map‐PD‐L1, membrane‐anchored‐protein PD‐L1; rgEC, rat glomerular endothelial cell

Fig 5: PI stimulation induces specific apoptosis of CD138+ T cells. (A) Flow cytometry analyses and bar charts demonstrating frequencies of apoptotic and live cells in CD3+CD138- and CD3+CD138+ T cells in splenocytes from MRL/lpr mice with or without 4 h PI stimulation. (B) Flow cytometry analyses and bar chart demonstrating the frequencies of apoptotic and live cells in CD138+CD3- plasma cells in splenocytes from MRL/lpr mice with or without 4 h PI stimulation. (C) Flow cytometry analyses and bar charts demonstrating CD69+ cell frequencies and FasL expression in CD3+ T cells in splenocytes from MRL/lpr mice with or without 4 h PI stimulation. (D) Flow cytometry analyses and bar charts demonstrating CD69+ cell frequencies in CD4+ T cells and DN T cells of splenocytes from MRL/lpr mice with or without 4 h PI stimulation. (E) Flow cytometry analyses and bar charts demonstrating CD69+ cell frequencies in CD138+ T cells of splenocytes from MRL/lpr mice after 0, 2, and 4 h PI stimulation. (F) Flow cytometry analyses and bar charts demonstrating FasL expression in CD138+, CD4+CD138+, and CD138+ DN T cells of splenocytes from MRL/lpr mice with or without 4 h PI stimulation. n=4-5 per group/experiment. *P<0.05 and **P<0.01 by one-way analysis of variance. MRL/lpr, Murphy Roths Large lymphoproliferative; PI, ionomycin; FasL, Fas ligand; DN, double negative; 7-AAD, 7-aminoactinomycin D; MFI, mean or median fluorescence intensity.