A total of 58 PMN patients admitted to the Department of Nephrology, the First Affiliated Hospital of Soochow University, from August 2021 to August 2023 were selected as the research subjects. Among the PMN patients, 40 individuals received RTX treatment and completed at least 6 months of follow-up.

The inclusion criteria for patients were as follows: (a) PMN diagnosed by renal biopsy; (b) aged 18–75 years; and (c) had complete baseline data, such as peripheral blood anti-PLA2R antibody titer and urine protein quantification.

The exclusion criteria for patients were as follows: (a) secondary membranous nephropathy caused by autoimmune diseases (such as hepatitis B virus infection, systemic lupus erythematosus, rheumatoid arthritis, etc.), malignant tumours, infections, drugs, etc.; (b) combined malignant tumours, blood system diseases, decompensated liver cirrhosis, heart failure, serious infections such as lung infection, peritonitis; (c) current active infection or combined with severe immunodeficiency diseases; (d) pregnant or (and) lactation; (e) rapidly progressive nephritis with severe renal impairment (eGFR < 15 ml/min/1.73 m2).

Twenty-five healthy age- and sex-matched people with an eGFR ≥ 60 ml/min/1.73 m2 and a negative urinary protein level who underwent physical examination at the health management centre of our hospital in 2021 were randomly selected as the healthy control group.

Flow cytometry was used to analyse the distribution of lymphocytes. Two millilitres of venous blood was collected from the two groups, stored at room temperature for 20 min and centrifuged at low speed (speed: 3500 r/min; radius: 8 cm). After 10 min, the upper serum sample was collected, ammonium chloride was used as the haemolysis agent, and then PBS (pH = 7.4, containing 0.5% BSA) was added after haemolysis. We centrifuged the cells twice every 5 min, after which the supernatant was discarded. Two tubes of 1 × 106 cells were added to two tubes of CDS dry powder for immune function and incubated at room temperature in the dark for 30 min. Then, we added PBS, centrifuged the cells, and washed them once every 5 min. The supernatant was discarded, and 500 µl of PBS (pH = 7.4, 0.5% PFA) was added to resuspend the cells. Flow cytometry was used to determine the distribution of peripheral blood lymphocytes, which included CD3+ T lymphocytes, CD3+CD4+ T cells, CD3+CD8+ T cells, mature NK cells (CD16+CD56+), B lymphocytes (CD3−CD19+), DNT cells (CD3+ CD4−CD8−), Treg cells (CD4+CD25+CD127lo), and CD4+CD25+ T cells. The kit used in this study was obtained from the German company Partec, and the testing instrument used was a CyFlowCube8 flow cytometer produced by the German company Partec. Finally, Kaluza analysis software was used to calculate the percentage of each lymphocyte subgroup among the peripheral blood lymphocytes based on the peripheral blood lymphocyte gates. The results of anti-PLA2R antibody titre and 24-hour urinary protein quantification were collected for all subjects before and after treatment.

Rituximab (Shanghai Fuhong Hanlin Biopharmaceutical Co., Ltd., National Drug Approval Number: S20190021, specification: 500 mg/50 ml) was injected by intravenous drip according to the following regimen:

Regimen 1: Standard-dose RTX 375 mg/m2 body surface area (BSA) was administered intravenously once every 2 weeks for a total of 4 doses.

Regimen 2: Standard dose of RTX (1 g/time, once every two weeks, intravenously, twice in total).

Regimen 3: Nonstandard dose of RTX 100 mg/time, once a week, 3 times in total.

Continuous variables were expressed as the mean ± standard deviation or median (quartile), and categorical variables were expressed as the number of patients (percentage). Independent sample t tests, nonparametric tests or chi-square tests were used to compare the differences between the data between groups. Correlations among variables were analysed by Spearman correlation. P < 0.05 was considered to indicate statistical significance, and the statistical analysis of the data was carried out with Microsoft version SPSS 23.0.