Immunoproteasome subunit LMP7 induction in tubular epithelial cells from SLE patients with nephritis. Increased expression of LMP7 was found in renal biopsies of patients with class IV lupus nephritis (B,D) compared to those with class I (A,C). LMP7 expression was found at the tubular interstitial level but not on glomerular cells (G) and vessels (V). Co-localization of LMP7 (red H, K) and MXA (green G, J) in tubular epithelium of patients with lupus nephritis was investigated by immunofluorescence/confocal microscopy (E-L). We found co-localization of LMP7 and MXA in class IV lupus nephritis (F,I,L) but not in class I, where MXA was absent and LMP7 had very low expression (E); nuclei were stained with TO-PRO-3 (blue); (L) zoom of figure F. (M) Quantification of immunohistochemical staining was carried out as described in Methods section. The histograms represent the increased tissue expressions of MXA (P <0.0001) and LMP7 proteins (P <0.0001) in eight class IV lupus nephritis patients compared to eight patients of class I/II. SLE, systemic lupus erythematous.