MHCII ⁺ monocytes are present in the urine of patients with active lupus nephritis, and their frequency correlates with disease activity. (A) Cumulative percentage of MHCII^hi cells within the CD14⁺CD163⁺ population in blood from healthy donors (HD) and patients with active lupus nephritis (LN; left) and lupus patients with high and low proteinuria (right). (B) Correlation of percentage of blood MHCII⁺ monocytes and disease index activity (SLEDAI). (C) Cumulative data and representative gating strategy showing the percentages of CD14⁺CD163⁺ cells within the live CD45⁺ cells (left panel) and MHCII^hi cells within the CD14⁺CD163⁺ population in urine from patients with active LN (right panel), separated based on the level of proteinuria (≥532 mg/24 h = high proteinuria). *, P < 0.05. FSC, forward scatter. (D) The correlation of percentage urine MHCII^hi monocytes and SLEDAI is shown.