title: Urinary free light chain is a potential biomarker for ISN/RPS class III/IV lupus nephritis.
abstract: OBJECTIVE
  To evaluate the use of urinary free light chains (FLCs) as a biomarker for proliferative LN and the potential association between the intensity of plasma cell infiltration of the kidney and urinary FLC levels in LN.
  
  
  METHODS
  Forty-three SLE patients were consecutively enrolled in the study. These patients were divided into an International Society of Nephrology and Renal Pathology Society (ISN/RPS) class III/IV LN subset (n = 18) and an ISN/RPS class I/II/V (class non-III/IV) LN subset (n = 25). The expression of κ-LCs, λ-LCs, CD19 and CD138 in kidney specimens was also evaluated with immunohistochemical staining. To measure FLC levels before and after treatment, an additional six patients with class III/IV LN were consecutively enrolled.
  
  
  RESULTS
  Urinary FLCs were significantly higher in the class III/IV LN subset than in the class non-III/IV LN subset. Urinary λ-FLC levels were significantly correlated with the urinary protein-creatinine ratio in the class III/IV LN subset (rs = 0.67, P < 0.01). Moreover, the LC-secreting CD19(-)/CD138(+) cell counts in the kidney specimens were higher in the class III/IV LN subset than in the class non-III/IV LN subset. Total urinary FLC levels were correlated with the numbers of CD138(+) cells in the kidney (r = 0.71, P = 0.03). Following treatment, urinary λ-FLCs could not be detected in any of the patients.
  
  
  CONCLUSIONS
  The intensity of plasma cell infiltration of the kidney is associated with urinary FLC levels. Urinary FLCs are potentially useful biomarkers in ISN/RPS class III/IV LN or proliferative LN.
authors: Institute of Rheumatology, Tokyo Women's Medical University, 10-22 Kawada-cho, Shinjuku-Ku, Tokyo 162-0054, Japan. tgono@ior.twmu.ac.jp.
authors: Masanori
authors: M
authors: Hanaoka
authors: Takahisa
authors: T
authors: Gono
authors: Yasushi
authors: Y
authors: Kawaguchi
authors: Keiko
authors: K
authors: Uchida
authors: Yumi
authors: Y
authors: Koseki
authors: Yasuhiro
authors: Y
authors: Katsumata
authors: Hirotaka
authors: H
authors: Kaneko
authors: Kae
authors: K
authors: Takagi
authors: Hisae
authors: H
authors: Ichida
authors: Kosaku
authors: K
authors: Nitta
authors: Hisashi
authors: H
authors: Yamanaka
mesh_terms: D018941:Antigens, CD19 / Q000378:metabolism; D015415:Biomarkers / Q000097:blood / Q000652:urine; D003404:Creatinine / Q000652:urine; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000097:blood / Q000652:urine*; D007150:Immunohistochemistry; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D008181:Lupus Nephritis / Q000145:classification / Q000175:diagnosis* / Q000188:drug therapy; D053668:Syndecan-1 / Q000378:metabolism
chemical_list: D018941:Antigens, CD19; D015415:Biomarkers; D007147:Immunoglobulin Light Chains; D007166:Immunosuppressive Agents; D053668:Syndecan-1; D003404:Creatinine
keywords: disease activity; free light chain; lupus nephritis; plasma cell