Background: Lupus nephritis (LN) is a severe manifestation of systemic lupus erythematosus (SLE), characterised by unpredictable outcomes due to the absence of reliable biomarkers. This hypothesis-generating study aimed to evaluate whether changes in the N-glycosylation of IgG, C3, AGP, and the serum proteins over one year of treatment correlate with clinical and histological features of LN and predict renal outcomes. Methods: Serum samples from 19 treatment-naïve patients with LN were collected at baseline and 12 months post-treatment, in conjunction with per-protocol repeat kidney biopsy. IgG (Fc, Fab, and total), C3, AGP, and total serum glycoproteins were isolated and analysed as either released N-glycans or N-glycopeptides using high-throughput glycomic approaches. Clinical and histological data were obtained at both time points, along with assessments of clinical and histological response at 12 months and long-term renal function. Results: In total, we identified 24/243 increased N-glycosylation traits (2 total IgG, 5 IgG Fc, 7 IgG Fab, 5 serum glycoproteins, 4 AGP, and 1 C3) and 10/243 decreased N-glycosylation traits (7 total IgG, 2 IgG Fc, 1 IgG Fab) following treatment. Baseline AGP IORMIF1N5H6S2F1 showed a positive correlation with eGFR both at baseline (r = 0.64, p = 0.005) and at 12 months (r = 0.51, p = 0.032). Among AGP N-glycosylation traits, IVORMI1N7H8S3 (r = 0.66, p = 0.002; r = 0.48, p = 0.041, respectively), VORMI1N8H9S4 (r = 0.51, p = 0.029; r = 0.49, p = 0.038, respectively), and VORMI1N8H9S4F1 (r = 0.48, p = 0.039; r = 0.49, p = 0.034, respectively) significantly correlated with activity index (AI) at baseline and at 12 months. Presence of cellular crescents at baseline positively correlated with three AGP N-glycosylation traits: IORMISORMIIA1N4H5S2 (r = 0.49, p = 0.036), VORMII1N5H6S3F1 (r = 0.63, p = 0.006), and VORMII1N4H5S2 (r = 0.48, p = 0.046). Total serum N-glycan (structure) N5H4F1 at 12 months was associated with both clinical and histological response to treatment. Delta of total serum N-glycan structure N5H5S1 was independently associated with poor long-term outcome. Conclusions: This study suggests that glycosylation changes over one year of treatment are associated with specific clinical and histological features and both short- and long-term renal outcomes in LN. Given the small cohort size, results should be considered hypothesis-generating warranting further investigation in independent cohorts.

The manuscript demonstrates that the activity of cytokine blocking antibodies can be enhanced by introducing a highly sialylated IgG Fc-domain.