# Peripheral blood B-cell compartment dysregulation in multidrug-resistant tuberculosis is associated with reduced circulating marginal zone-like B cells

## TL;DR

The study finds that people with active tuberculosis have fewer specific types of B cells, suggesting immune system changes that could help diagnose the disease.

## Contribution

The paper identifies reduced circulating marginal zone-like B cells as a novel feature of active tuberculosis.

## Key findings

- Active tuberculosis is associated with reduced frequencies of total CD19+ B cells and antibody-secreting cells.
- Circulating marginal zone-like B cells are significantly reduced in active tuberculosis compared to non-active groups.
- Reduced marginal zone-like B cells may help distinguish active tuberculosis cases, though further research is needed.

## Abstract

Multidrug-resistant tuberculosis (MDR-TB) remains a major global health challenge. While T cell-mediated immunity in tuberculosis is well characterized, alterations in circulating B-cell subsets during chronic MDR-TB are less well defined.

Peripheral blood mononuclear cells (PBMCs) from healthy controls [interferon gamma release assay negative (IGRA−)], individuals with latent tuberculosis infection (LTBI; IGRA+), and patients with active tuberculosis (ATB) were analyzed using multiparameter flow cytometry panels. Major lymphoid and myeloid populations and detailed B-cell subsets were quantified.

Frequencies of major T-cell and natural killer (NK)-cell populations were broadly similar across groups. In contrast, patients with ATB showed a reduction in total CD19+ B cells. Within the B-cell compartment, ATB was characterized by an increased proportion of naïve B cells and a pronounced reduction in antibody-secreting cells (ASCs). Circulating marginal zone-like B cells (MZ B, IgD+IgM+CD27+) were also reduced in ATB compared with non-ATB groups. Receiver operating characteristic (ROC) analysis suggested that reduced MZ B-cell frequency may help discriminate individuals with ATB from those without ATB; however, this observation should be interpreted as exploratory given the cohort size and composition.

MDR-TB is associated with broad perturbations of the peripheral B-cell compartment, including reduced ASCs and decreased circulating MZ B cells. These findings highlight B-cell dysregulation as a feature of active disease and identify MZ B cells as a subset of interest for further investigation rather than as a stand-alone diagnostic marker.