Baseline data of different groups

This study included three groups to evaluate the effects of Belimumab (BLM) on the changes in peripheral blood lymphocyte subsets and cytokines in children with systemic lupus erythematosus (JSLE). The BLM group had 36 patients, the traditional treatment group had 35, and the control group included 30 healthy individuals. As detailed in Table 1, there were no significant differences in age, gender, or BMI among the three groups (all P > 0.05).

Table 1 Baseline data of enrolled study patientsExpression of inflammatory cytokines

Data for peripheral blood lymphocyte subsets and cytokines did not meet the sphericity assumption and were asymmetrical (P < 0.001). Therefore, Roy’s largest root test was used for analysis, and significant interaction effects between treatment time points and group (P < 0.001) were observed. More details are shown in Table 2 and Fig. 1.

Table 2 The changes in cytokine levels at different time points before and after the use of BelimumabFig. 1

The expression levels of inflammatory cytokines in the BLM group and the conventional treatment group at different treatment time points. (A) IL-2; (B) IL-10; (C) IL-21; (D) IL-35; (E) IFN-γ

IL-2

Both the BLM and traditional treatment groups showed significant differences compared to the control group (both P < 0.05), but no significant difference was found between the two treatment groups (P = 0.055). Simple effect tests at different time points showed significant differences before treatment (F = 7.670, P = 0.007), at 6 months (F = 74.971, P < 0.001), and at 12 months (F = 41.914, P < 0.001), while no significant difference was observed at 6 weeks (Z = 1.912, P = 0.056). Both treatment groups showed significant effects across different time points (BLM: F = 851.157, P < 0.001; traditional treatment: F = 634.801, P < 0.001), with all pairwise comparisons showing statistical significance (all P < 0.05).

IL-10

Before treatment, there were significant differences in IL-10 levels between the groups (P < 0.001). Both treatment groups showed significant differences compared to the control group (both P < 0.05), but no significant difference was found between the two treatment groups (P = 0.896). Simple effect tests at various time points revealed significant differences after 6 weeks (F = 24.473, P < 0.001), 6 months (F = 86.703, P < 0.001), and 12 months (F = 25.816, P < 0.001), while no significant difference was observed before treatment (F = 0.399, P = 0.530). Both the BLM and traditional treatment groups showed significant effects across different time points (BLM: F = 721.126, P < 0.001; traditional treatment: F = 404.170, P < 0.001), with all pairwise comparisons showing statistical significance (all P < 0.05).

IL-21

There was a significant difference in IL-21 expression before treatment among the groups (P < 0.001). All group pairwise comparisons showed significant differences (all P < 0.05). Simple effect tests revealed significant differences before treatment (F = 6.722, P = 0.011), at 6 months (F = 46.247, P < 0.001), and 12 months (F = 21.449, P < 0.001), while no significant difference was observed at 6 weeks (F = 0.398, P = 0.530). Both treatment groups showed significant effects across different time points (BLM: F = 467.153, P < 0.001; traditional treatment: F = 409.464, P < 0.001), with all pairwise comparisons showing statistical significance (all P < 0.05).

IL-35

IL-35 levels before treatment differed significantly between groups (P < 0.001), with pairwise comparisons showing differences between all groups (all P < 0.05). Simple effect tests at different time points showed significant differences before treatment (F = 7.393, P = 0.008), at 6 weeks (F = 20.484, P < 0.001), 6 months (F = 119.149, P < 0.001), and 12 months (F = 25.546, P < 0.001). Both treatment groups showed significant effects at different time points (BLM: F = 267.347, P < 0.001; traditional treatment: F = 269.796, P < 0.001), with all pairwise comparisons showing statistical significance (all P < 0.05).

r-Interferon

Before treatment, there were significant differences in r-interferon levels between groups (P < 0.001). However, no significant difference was found between the treatment groups (P = 0.821). Simple effect tests showed significant differences at 6 months (F = 32.054, P < 0.001) and 12 months (F = 68.243, P < 0.001), but not before treatment (F = 0.118, P = 0.732) or at 6 weeks (Z = 1.950, P = 0.051). Both treatment groups showed significant effects across different time points (BLM: F = 874.069, P < 0.001; traditional treatment: F = 811.189, P < 0.001), with all pairwise comparisons showing statistical significance (all P < 0.05).

Peripheral blood lymphocyte subset Breg cell detection CD3 + CD19 + B cells

Except for before treatment, where there was no significant difference between groups (F = 0.103, P = 0.750), significant group effects were found at 6 weeks (F = 55.531, P < 0.001), 6 months (F = 300.332, P < 0.001), and 12 months (F = 249.205, P < 0.001). In the BLM group, the relative values decreased significantly across all time points (all P < 0.001), with significant differences at each time point (F = 136.489, P < 0.001). In the traditional treatment group, the relative values also decreased significantly across time points (F = 37.178, P < 0.001), with all comparisons showing statistical significance (all P < 0.001). Detailed test results are shown in Table 3.

Table 3 The relative changes in different Breg cells at different time points before and after the use of Belimumab CD27 + CD24 + B cell count

Before treatment, no significant differences were found between the groups (P = 0.066), and pairwise comparisons also showed no significant differences (P > 0.05). At 6 weeks (F = 14.048, P < 0.001) and 12 months (F = 21.299, P < 0.001), significant group effects were found, whereas no significant difference was observed between the two treatment groups at 6 months (P > 0.05). In the BLM group, significant differences were observed at all time points (F = 94.216, P < 0.001), with all comparisons showing statistical significance (all P < 0.001). In the traditional treatment group, significant differences were found except between the third and fourth-time points (P > 0.05), with all other comparisons showing significance (all P < 0.001) (Table 3 and Fig. 2).

Fig. 2

The relative expression levels of peripheral blood lymphocyte Breg cell subsets in the BLM group and the conventional treatment group at different treatment time points. (A) CD3⁻CD19⁺ B cells; (B) CD27⁺CD24⁺ B cells; (C) CD38⁺CD24⁺ B cells; (D) CD38⁺CD19⁺ B cells

CD38 + CD24 + B cells

Before treatment, no significant differences were found between the groups (All P > 0.05).

At 6 months (F = 18.031, P < 0.001) and 12 months (F = 54.714, P < 0.001), significant group effects were observed. In the BLM group, there were significant differences at all time points (F = 33.296, P < 0.001), with all comparisons showing statistical significance (all P < 0.05). In the traditional treatment group, significant differences were found at the first time point compared to the others (P < 0.05). In contrast, no significant differences were observed between the 2nd, 3rd, and 4th time points (P > 0.05).

CD38 + CD19 + B cells

Before treatment, there were significant differences between the groups (P < 0.001), with both the BLM and traditional treatment groups showing differences compared to the control group (both P < 0.05). Significant group effects were found at 6 weeks (F = 7.300, P = 0.009), 6 months (F = 64.367, P < 0.001), and 12 months (F = 67.492, P < 0.001). In the BLM group, significant differences were found at all time points (F = 491.492, P < 0.001), with all pairwise comparisons showing statistical significance (all P < 0.05). In the traditional treatment group, significant differences were observed at all time points (F = 274.390, P < 0.001), with all comparisons showing statistical significance (all P < 0.05) (Table 3).

Adverse events and organ involvements

In the traditional treatment group, 10 cases of irregular oral medication led to disease flare-ups, with 5 cases of lupus nephritis (2 III + type, 3 IV + V types), 2 cases of neuropsychiatric lupus, 2 cases of autoimmune hemolysis, and 1 case of mesenteric vasculitis. In this group, 5 cases had negative antinuclear antibody (ANA) results, 30 maintained high ANA titers, and five patients stopped glucocorticoid therapy. In the BLM group, glucocorticoid (GC) doses were reduced to ≤ 2.5 mg/d within 1 year, with 4 cases of ANA negativity and 32 cases maintaining high ANA titers. All 54 patients stopped GC therapy, and during the treatment with rituximab (20–25 mg/kg/d), no disease activity or relapse was observed (Table 3).

Among the organ involvements, central nervous system involvement was observed in 8 patients in the conventional treatment group and 10 patients in the BLM group. Renal involvement was present in 23 patients in the conventional group and 20 in the BLM group. Hematologic involvement was noted in 7 patients in the conventional group and 12 in the BLM group. Abnormal respiratory manifestations were observed in 7 patients in the conventional group and 4 in the BLM group. Cardiovascular involvement occurred in 2 patients in the conventional group and 5 in the BLM group. Gastrointestinal adverse manifestations were reported in 4 patients in the conventional group and 2 in the BLM group. Thyroid involvement was found in 1 patient in the conventional group and none in the BLM group. Macrophage activation syndrome was reported in 3 patients in both the conventional and BLM groups. Detailed results are presented in Table 4.

Table 4 Organ/diseases involvement in pediatric patients of both treatment groupsTherapeutic effect

We used the SLEDAI score and the SID score to assess disease activity in systemic lupus erythematosus (SLE) and the severity of systemic inflammatory response, respectively. After 1 year of treatment, the comparison between the two groups showed that the ANA seroconversion rate was 44.44% (16/36) in the BLM group and 17.14% (6/35) in the conventional group. Additionally, 77.14% (27/35) of patients in the conventional group achieved the Lupus Low Disease Activity State (LLDAS), while 85.71% (30/36) of patients in the BLM group met the LLDAS criteria. Although there was an apparent numerical difference between the two groups after 1 year of treatment (3.17 in the control group vs. 2.00 in the experimental group), repeated measures ANOVA revealed no statistically significant between-subjects effect (F = 2.506, P = 0.118), and the time × group interaction effect was also not significant (F = 0.018, P = 0.895). These findings indicate that while the experimental group showed greater numerical improvement, the overall change patterns over time were not significantly different between the two groups. Detailed results are presented in Table 5.

Table 5 Comparison of SLEDAI and SID scores before and after treatment between the two groups