As Autoimmune Therapies Evolve, Immune Monitoring Must Too

For decades, the goal of autoimmune disease treatment has been to suppress immune activity, control symptoms, and slow disease progression. A new generation of B-cell-depleting therapies (BCDTs), however, is raising a more ambitious possibility: long-term, drug-free remission through a process thought to resemble an immune reset.

Emerging approaches such as T-cell engagers (TCEs) and chimeric antigen receptor (CAR) T-cell therapies can achieve substantially deeper depletion of pathogenic B cells, including tissue-resident B-cell populations thought to be less accessible to conventional antibody therapies.

As these therapies advance through clinical development, they are not only reshaping treatment expectations but also redefining what researchers need to measure to determine whether a therapy has truly been successful.

This shift is driving new demands in immune monitoring. Rather than simply quantifying circulating B cells, researchers increasingly need to understand the depth of B-cell depletion, the kinetics of immune reconstitution, and whether the recovering immune system reflects a genuine immune reset.

Technology Networks spoke with Dr. Céline Vandamme, scientific business director at CellCarta, to find out how advances in BCDTs are transforming autoimmune disease treatment, and why highly sensitive, standardized immune monitoring will be essential to support the next generation of clinical trials.

Deep B-cell depletion is reshaping autoimmune disease treatment

BCDTs are reshaping the treatment landscape in autoimmune disease. From your perspective, what is driving this shift, and how is it changing the way we think about immunological monitoring?

"Disrupting the pathogenic autoreactive B-cell and T-cell collaboration in autoimmune diseases using BCDTs is not a novel approach," Vandamme emphasized.

What is changing is the depth and durability of B-cell depletion that can now be achieved.

Earlier CD19- and CD20-targeting monoclonal antibodies have become established standards of care across several autoimmune diseases, but long-term clinical responses have often been variable. According to Vandamme, newer therapeutic modalities are overcoming many of these limitations by producing substantially deeper depletion of B-cell populations, including pathogenic subsets.

"This phase of deep B-cell aplasia is followed by a repopulation phase, during which the reemergence of only naïve/transitional B cells is currently thought to indicate an 'immune reset' that supports the promising drug-free remission rates observed with these novel therapeutic modalities," she said.

For researchers and clinicians, this represents an important shift in how therapeutic success is defined. Assessing efficacy is no longer solely about confirming that B cells have been depleted; it increasingly depends on understanding how the immune system recovers following treatment, whether that recovery reflects a true immune reset, and how long remission will last.

Why deep B-cell depletion is changing treatment expectations:

• Emerging BCDTs are achieving substantially deeper depletion of pathogenic B cells than earlier therapies.
• Eliminating tissue-resident B-cell populations may help explain the durable remissions reported with next-generation therapies.
• Immune monitoring is evolving beyond measuring depletion alone to understanding immune reconstitution and long-term immune reset.

As therapies improve, immune monitoring must become more sensitive

Flow cytometry is considered the gold standard for B-cell monitoring. Why is it so challenging to reliably detect and distinguish B-cell populations during depletion and early immune reconstitution?

The remarkable efficacy of next-generation BCDTs is creating an unexpected challenge for researchers. As treatments achieve increasingly profound depletion of pathogenic B cells, detecting the few cells that remain—and accurately tracking their return—has become significantly more difficult.

Flow cytometry has long been considered the gold standard for monitoring B-cell populations in clinical studies. However, Vandamme explained that conventional assays were not designed to measure the exceptionally low cell frequencies now being observed with emerging therapies.

"As frequencies of peripheral B cells fall well below 1 cell/µL of blood during treatment, the reliable detection and distinction of B-cell populations can become challenging due to the lack of precision and stability of the standard enumeration assays used to determine B-cell counts," she said.

At these extremely low concentrations, even small sources of analytical variability can influence results. Distinguishing between complete B-cell aplasia and the earliest stages of immune reconstitution, therefore, requires assays capable of detecting very rare cell populations with a high degree of confidence.

"Improving the detection sensitivity of these assays, which effectively translates to lowering the lower limit of quantification for B cells, requires optimizing the methodology in a way that also satisfies 1) internationally recognized guidelines for flow cytometry assay validation (such as CLSI H62), 2) operational feasibility in the analytical lab, and 3) compatibility with large-scale clinical implementation to support secondary endpoints or patient management decision-making," Vandamme added.

As therapeutic strategies continue to evolve, assay development is becoming an increasingly important component of clinical research. The ability to reliably detect profound B-cell depletion and characterize immune recovery may ultimately determine how confidently researchers can assess whether an immune reset has occurred.

Why assay sensitivity matters:

• Emerging BCDTs are pushing peripheral B-cell counts below the detection limits of many conventional assays.
• Detecting the earliest stages of immune reconstitution requires highly sensitive and reproducible flow cytometry methods.
• Improved assay sensitivity must be matched by the robustness needed for large, multicenter clinical trials.
  

Harmonizing B-cell monitoring approaches to improve reproducibility

How does variability in marker selection and gating strategies affect reproducibility and cross-study comparability?

As B-cell-targeting therapies continue to evolve, so too must the approaches used to monitor immune responses. One emerging challenge is ensuring that flow cytometry strategies remain comparable across different clinical programs, particularly as increasingly complex therapeutic designs enter development.

Vandamme highlighted that BCDTs are rapidly expanding beyond single-target approaches, such as CD19 or CD20 targeting, toward dual- and tri-target strategies involving combinations such as CD19/CD20, CD19/BCMA, and CD19/CD20/BCMA.

While these advances provide new opportunities for therapeutic intervention, they also introduce analytical challenges, as therapeutic antibodies can alter the availability of traditional B-cell markers used for monitoring.

"To be able to compare drug efficacy across all programs, it is imperative to understand how different B-cell gating strategies compare so that we can have flexibility in marker selection when certain classical B-cell epitopes are masked," Vandamme explained.

Developing a more harmonized approach to gating will therefore be increasingly important as the field progresses. Standardized strategies can help ensure that results generated across studies remain interpretable, enabling more meaningful comparisons of therapeutic efficacy and immune recovery.

Why harmonized gating strategies matter for B-cell monitoring:

• Increasingly complex multi-target therapies are creating new analytical challenges.
• Therapeutic target engagement may interfere with conventional B-cell marker detection.
• Consistent gating approaches are essential for reproducible data generation across clinical programs.

Reliable immune monitoring requires end-to-end standardization

Beyond assay design, what are the key operational and logistical challenges in maintaining sensitivity and consistency in longitudinal, multicenter B-cell monitoring studies?

Generating high-quality immune monitoring data requires more than a robust analytical assay.

"To maintain sensitivity and consistency, standardization is needed throughout the entire sample lifecycle to minimize pre-analytical sample variability, inter-assay variability, and inter-analyst variability," Vandamme explained.

This requires careful control at every stage of the workflow, from sample collection and processing through to data analysis and interpretation. Even highly sensitive technologies can produce inconsistent results if variability is introduced earlier in the process.

Vandamme emphasized the role of comprehensive quality frameworks in supporting reliable immune monitoring studies. A robust quality management system, she explained, should incorporate standardized operating procedures, harmonized instrumentation, operator qualification, and centralized data analysis.

As clinical studies become increasingly complex and geographically distributed, maintaining this level of operational consistency will be essential for generating reliable longitudinal datasets and enabling confident interpretation of immune monitoring results.

How operational standardization supports data quality:

• Variability can be introduced at multiple points throughout the testing workflow.
• Consistency is required across sample handling, analysis, and interpretation.
• Strong quality management systems help ensure reliable, high-quality data across multicenter studies.
  

Multiomics approaches could redefine immune reset

Looking ahead, what advances do you expect will most significantly improve B-cell monitoring in autoimmune therapies?

As B-cell-targeting therapies continue to demonstrate the potential to induce long-lasting remission in autoimmune disease, researchers are increasingly looking beyond traditional measures of immune reconstitution to better understand why some patients achieve durable responses.

"Perhaps one of the most impactful factors for improving B-cell monitoring in autoimmune therapies, particularly as it pertains to the prediction of relapse, will be the 'refinement' of the definition of immune reset," Vandamme said.

Currently, immune reset is often assessed through changes in naïve and memory B-cell populations. However, as longer-term clinical data accumulate, it is becoming clear that these phenotypic markers alone may not fully capture the biological processes underlying treatment response.

Vandamme highlighted that current definitions of immune reset may not always align with clinical outcomes, noting that "there is evidence that immune reset, or at least the way that it is predominantly defined now with naïve/memory phenotyping markers, does not always correlate with prolonged clinical improvement."

This has prompted interest in broader approaches that integrate multiple layers of immune biology. Rather than relying on a single set of surface markers, combining complementary measurements could provide a more comprehensive view of immune recovery and help identify biomarkers that better predict therapeutic efficacy and long-term remission.

"A multiomics approach, combining naïve/memory phenotyping markers, plasma cell assessment, autoreactive B-cell measurement, serology, and single-cell BCR sequencing, for example, might yield a better predictor of clinical efficacy and long-term outcome," Vandamme explained.

Another important area of development will be determining whether peripheral B-cell measurements can serve as a reliable surrogate for depletion of tissue-resident B cells. Establishing a regulated threshold for peripheral B-cell aplasia could provide a clinically useful biomarker, but additional evidence will be needed to define the relationship between circulating and tissue-resident immune populations.

Vandamme emphasized the need for studies correlating peripheral and tissue B-cell assessment, both quantitatively and qualitatively, using high-sensitivity flow cytometry and histopathology assays on paired blood and tissue biopsies.

As immune monitoring continues to evolve, integrating multiomic approaches with high-sensitivity cellular analysis could provide a more meaningful framework for defining immune reset and predicting long-term patient outcomes. Ultimately, this could chart a path towards mapping the best therapy for each patient.

Where the future of immune monitoring is headed:

• Current definitions of immune reset may not fully reflect clinical response.
• Multiomics approaches could provide a more comprehensive view of immune recovery.
• Peripheral B-cell aplasia thresholds may help establish surrogate biomarkers for tissue-level depletion.