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Urinary T-cells remain useful biomarker for lupus nephritis
Although B-cells and macrophages are detectible in urine, urinary T-cells remain the most important biomarker of lupus nephritis, according to researchers at the Charité University Hospital in Berlin.
From April 2009 and March 2013, the researchers compared the results of urine analyses from 19 patients with systemic lupus erythematosus (SLE) and active renal involvement with 79 patients with SLE and no renal involvement, 74 patients with diabetic nephropathy and 11 patients with anti-neutrophil cytoplasmatic antibody (ANCA) associated vasculitis (AAV). Eight patients with AAV had granulomatosis with polyangiitis (formerly known as Wegener’s granulomatosis), and all had associated renal involvement. Disease activity in patients with AAV was assessed using the Birmingham Vasculitis Activity Score (BVAS).
The Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) scores were calculated for all patients with SLE. Active renal involvement was defined by high disease activity (SLEDAI > 10) and a kidney biopsy taken within the previous 4 weeks, or the presence of at least two renal elements of the SLEDAI.
The analysis of urinary calls was completed in 71 patients with SLE, and urinary T-cell subset analysis was conducted with 53 of the patients with SLE. Patients with SLEDAI of 10 or higher and biopsy-confirmed lupus nephritis had high numbers of both CD4+ (median 1,415 cells/dL) and CD8+ (median 1,911 cells/dL) T-cells, as well as higher numbers of CD14+ macrophages (median 33,808 cells/dL). Only moderate increases in CD19+ B-cells were seen in 10 patients with active renal involvement, according to the researchers.
Low numbers of T-cells (CD4+: median 29 cells/dL; CD8+: 25 cells/dL) and CD19+ B-cells were detected in patients with SLE and no active renal symptoms, but CD14+ counts were high (264 cells/dL). Disease activity based on SLEDAI scores correlated with the presence of CD3 + CD4+, CD3 + CD8+, CD14+ and CD19+ cells, the researchers found.
Patients with diabetic nephropathy showed moderate levels of CD4+ (median 262 cells/dL) and low levels of CD8+ (median 82 cells/dL) and CD19+ B-cells (median 69 cells/dL), but high levels of CD14+ macrophages (median 3,770 cells/dL).
Variable lymphocyte counts were seen in patients with AAV, with macrophages detected in all samples, and no correlation was seen between cell counts and BVAS, according to the researchers.
The ratio of CD4+ and CD8+ was calculated for all patients with at least 100 CD3+ cells/dL, which included 38 patients with SLE, 11 patients with diabetic nephropathy and seven patients with AAV. Patients with severe diabetic nephropathy showed reciprocal proportions, a difference from patients with SLE that was significant. A comparison of ratios between patients with AAV and SLE revealed no significant differences.
The researchers concluded that the presence of high levels of T-cells in the urine of patients with SLE was a reliable indicator of active lupus nephritis. - by Shirley Pulawski
Disclosure: The researchers report no relevant financial disclosures.