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Introduction: It has been recognized that T cells have a pathogenic role in anti-neutrophil cytoplasmic antibody- (ANCA) associated vasculitis, in addition to being dominant cells in the interstitium in ANCA glomerulonephritis (GN). Given there are differences in renal outcomes based on ANCA type, we sought to characterize the interstitial infiltrate in ANCA GN to determine differences in relation to ANCA type and renal function., Methods: Immunohistochemistry stains for CD3, CD4, CD20, C4d and FOXP3 were done in renal biopsies of patients with ANCA GN. Light microscopy was used to determine the percentage of cortical interstitium containing positive cells. Demographics, ANCA type and entry eGFR were recorded. The level of staining was compared between ANCA type and entry eGFR using Wilcoxon rank-sum test., Results: Renal biopsies of 16 patients with MPO and 14 with PR3 ANCA GN were studied. CD3 cells were the predominant cells, with all biopsies staining positive for CD4 and FOXP3. C4d staining was negative in all biopsies, with no significant difference in staining between MPO and PR3 groups for any of the identified cell types. However, regardless of ANCA type, FOXP3 staining was significantly higher in patients with baseline GFR < 10 compared with GFR > 10 mL/min/1.73 m 2 (mean 7.54, SD 6.6 versus mean 2.67, SD 3.6; p = 0.04)., Conclusion: These data confirm the role of T cells in ANCA GN and demonstrate no differences in interstitial T and B cell infiltrates between PR3 and MPO ANCA GN. Higher FOXP3 signal associates with lower renal function, suggesting a role for regulatory T cells. Further characterization of this T cell subset should be explored in future studies., (© 2021. Italian Society of Nephrology.)

Background: Kidney involvement is common in patients with systemic lupus erythematosus (SLE). This study investigates the clinical and prognostic characteristics of thrombotic microangiopathy (TMA) compared to class IV lupus nephritis in SLE patients., Methods: A retrospective review of patients who underwent kidney biopsy, with a primary diagnosis of SLE and TMA between June 2006 and September 2018 was conducted. Those patients were subsequently compared to patients with class IV lupus nephritis between January 2018 and December 2018. Demographics, laboratory, and serological data at the time of biopsy were abstracted., Results: Among 214 SLE patients records screened, 27 were included in the final analysis. Eight patients had lupus-related TMA without evidence of active lupus nephritis, while 19 patients had class IV lupus nephritis without evidence of TMA. TMA patients had significantly higher lactate dehydrogenase levels (718 ± 499 vs. 264 ± 107.7 U/L, p = 0.009), serum C3 (100.6 ± 39.3 vs. 65.8 ± 27 mg/dL, p = 0.049), white blood cell count (14743.8 ± 7933.3 vs. 5807.9 ± 2053.2 × 10E3/uL, p < 0.001), and total bilirubin (0.8 ± 0.5 vs. 0.3 ± 0.1 mg/dL, p = 0.007) in addition to significantly lower platelet counts (158.4 ± 88.6 vs. 240.3 ± 100.3 × 10E3/uL, p = 0.03), and haptoglobin (68.8 ± 116.1 vs. 166.8 ± 95.4 mg/dL, p = 0.03). After a median follow-up time of 53 weeks, 3 patients with TMA were dialysis-dependent (37.5%), compared with none in class IV lupus nephritis patients (p = 0.002)., Conclusions: TMA-associated SLE has worse prognosis compared to class IV lupus nephritis. An array of laboratory and pathological findings may be of value in discriminating between those two entities., (© 2021. Italian Society of Nephrology.)