# Alternation in Peripheral B Cell Subpopulations Is a Potential Biomarker for Autoimmune Diseases—A Cross-Sectional Study

## TL;DR

Changes in B cell subpopulations in the blood may help diagnose and assess autoimmune diseases, with higher levels seen in patients compared to healthy individuals.

## Contribution

This study identifies altered B cell subpopulations as a potential biomarker for autoimmune diseases using a novel scoring system.

## Key findings

- Double-negative B cells and antibody-secreting cells were significantly higher in patients with autoimmune diseases.
- Systemic lupus erythematosus showed the most significant impact on B cell subpopulation changes.
- A scoring system effectively distinguished patients from healthy controls with 70.4% sensitivity and 70.8% specificity.

## Abstract

Background: Although autoimmune diseases differ in their pathogenesis, B cells play a central role in many of them, and alterations in peripheral B cell subpopulations have been observed. Therefore, we aimed to explore the possibility of peripheral B cell subpopulations as a biomarker for autoimmune diseases based on their alternation. Methods: We prospectively collected blood samples from 54 patients with various autoimmune diseases and 65 healthy controls. The percentages of B cell subpopulations were evaluated using flow cytometry. A scoring system was developed and the largest Youden’s index was used to determine the optimal cutoff point. Results: The frequencies of double-negative B cells and antibody-secreting cells were significantly higher in patients than in controls (median: 2.9% vs. 1.5%, p < 0.001; median: 3.6% vs. 2.1%, p = 0.001, respectively). Among the patients, those with systemic lupus erythematosus showed the most impact on the alteration of peripheral B cell subpopulations, which was correlated with disease activity. Furthermore, the scoring system effectively distinguished patients from healthy controls. The area under the receiver operating characteristic curves was 0.752 (95% confidence interval: 0.664–0.840), and the optimal cutoff value of ≥10 points yielded a sensitivity and specificity of 70.4% and 70.8%, respectively. Conclusions: Peripheral B cell subpopulations in patients with autoimmune diseases are significantly different from those in healthy individuals and can vary between diseases. Therefore, alterations in B cell populations may be a potential biomarker for diagnosing and evaluating autoimmune diseases.