Immunohistochemical expression of CD138 as a marker of B cell activity in renal biopsy in lupus nephritis patients

Abstract Background Lupus nephritis (LN) represents a significant complication of systemic lupus erythematosus (SLE) and can frequently lead to end-stage renal disease. Traditionally, attributed to immune complex deposition, recent evidence suggests a local renal immune mechanism plays a significant role. Among emerging biomarkers, Syndecan-1 (CD138), a transmembrane heparan sulfate proteoglycan is implicated in B cell function and tubular epithelial stress. The immunohistochemical expression of CD138 may provide additional insights into LN pathogenesis and disease monitoring. The purpose of this study is to examine the role of CD138 in LN by assessing its expression in kidney biopsies and analyzing its relationship with clinical, laboratory, and histopathological factors, such as SLE disease activity and LN chronicity indices. Methodology This cross-sectional study involved 21 patients with biopsy-confirmed LN (81% female; average age 27.7 ± 7 years). Immunohistochemical staining for CD138 was conducted on kidney biopsy samples and analyzed in relation to serum creatinine, proteinuria, complement levels, SLEDAI scores, anti-dsDNA antibody levels, and histological LN classification. Results CD138 expression in renal tubular epithelial cells significantly correlated with renal SLEDAI scores, higher proteinuria, elevated serum creatinine, low complement levels (C3, C4), and increased anti-dsDNA titers. No significant correlation was found with SLEDAI-2 K, BUN, UPCR, or biopsy activity/chronicity indices. Among biopsy classes, class IV was predominant (47.6%), followed by class II (23.8%), class III (19%), and class V (9.5%). Interstitial fibrosis and tubular atrophy was mild in 71.4%, moderate in 19%, and absent in 9.5% of patients. CD138 expression did not differ significantly across LN classes. Conclusion CD138 immunohistochemical expression in renal tubular epithelial cells represents a promising biomarker for disease severity in LN. Its correlation with renal-specific disease activity parameters supports its utility in identifying active nephritis and potentially predicting progression. Although not linked to biopsy class or chronicity indices, CD138 could still provide useful supplementary information for the histopathological assessment of LN.