Objective To analyze the reconstitution patterns of fine B-cell subsets in patients following treatment with the CD20 monoclonal antibody ofatumumab and the CD19 monoclonal antibody inebilizumab, and to evaluate the clinical application value of individualized fine B-cell subset dynamic profiling in guiding targeted therapy strategies.

Methods This prospective study enrolled 30 patients with pemphigus receiving ofatumumab and 26 patients with neuromyelitis optica spectrum disorders (NMOSD) receiving inebilizumab at West China Hospital of Sichuan University between October 2023 and May 2025. Thirty healthy individuals were enrolled as controls for baseline comparison. Dynamic monitoring of fine B-cell subsets, anti-desmoglein (Dsg) antibodies, and immunoglobulins was performed at three post-treatment time points (1 month, 3 months, and 6 months). A natural cubic spline model was used to fit trend curves, combined with differential analysis to assess population-level immune reconstitution.

Results At baseline (T0), patients in the pemphigus group had higher levels of several B-cell subsets compared to healthy controls. Total B-cell counts were 347.50 (250.40-621.8) cells/μL versus 217.50 (143.50-275.30) cells/μL, memory B-cell counts were 127.30 (74.63-196.70) cells/μL versus 57.00 (41.75-88.25) cells/μL, and plasmablast counts were 5.63 (2.02-11.48) cells/μL versus 1.00 (1.00-2.00) cells/μL. These differences were significant (P < 0.05). In contrast, NMOSD patients showed significantly higher plasmablast counts compared to healthy controls (2.07 1.60-3.58 cells/μL vs. 1.00 1.00-2.00 cells/μL) (P = 0.04). After three months, the proliferation rate of naive B cells increased, with counts rising from 0.95 cells/μL at T3 to 3.25 cells/μL at T6 (P = 0.001). Throughout the entire monitoring period, the proportion of memory B cells consistently remained higher than that of naive B cells and plasmablasts. In NMOSD patients, B-cell regeneration was slow after treatment. Total B-cell counts showed a significant increase only by T6 compared to T1 (from 0 cells/μL to 2.65 cells/μL, P = 0.026), with the increase primarily due to naive B cells. Plasmablast counts in the pemphigus group were significantly higher than those in the NMOSD group at T1 and T3 (P < 0.01), but this difference disappeared by T6. Among the cohort, two pemphigus patients showed abnormal B-cell reconstitution, characterized by persistently elevated plasmablasts or undetectable Dsg antibody decline. One NMOSD patient exhibited a reversal in B-cell subset proportions, with memory B-cell counts exceeding naive B-cell counts, along with increased plasma cell counts and elevated IgG immunoglobulin levels.

Conclusion Targeted therapies against CD19 and CD20 induce distinctly different patterns of B-cell reconstitution. Ofatumumab treatment leads to a phased regenerative process in B cells, whereas inebilizumab treatment results in delayed regeneration. Increased plasmablasts, aberrant memory B-cell proliferation, and rebounding Dsg antibodies may signal potential adverse events. These findings support monitoring fine B-cell subsets for precise immunological assessment to guide personalized treatment.