Thioredoxin is a metabolic rheostat controlling regulatory B cells.

Metabolic programming is important for B cell fate, but the bioenergetic requirement for regulatory B (Breg) cell differentiation and function is unknown. Here we show that Breg cell differentiation, unlike non-Breg cells, relies on mitochondrial electron transport and homeostatic levels of reactive oxygen species (ROS). Single-cell RNA sequencing analysis revealed that TXN, encoding the metabolic redox protein thioredoxin (Trx), is highly expressed by Breg cells, unlike Trx inhibitor TXNIP which was downregulated. Pharmacological inhibition or gene silencing of TXN resulted in mitochondrial membrane depolarization and increased ROS levels, selectively suppressing Breg cell differentiation and function while favoring pro-inflammatory B cell differentiation. Patients with systemic lupus erythematosus (SLE), characterized by Breg cell deficiencies, present with B cell mitochondrial membrane depolarization, elevated ROS and fewer Trx+ B cells. Exogenous Trx stimulation restored Breg cells and mitochondrial membrane polarization in SLE B cells to healthy B cell levels, indicating Trx insufficiency underlies Breg cell impairment in patients with SLE.

Diversity of regulatory B cells: Markers and functions.

Regulatory B cells (Bregs) are a functionally distinct B-cell subset involved in the maintenance of homeostasis and inhibition of inflammation. Studies, from the last two decades, have increased our understanding of cellular and molecular mechanisms involved in their generation, function, and to a certain extent phenotype. Current research endeavours to unravel the causes and consequences of Breg defects in disease, with increasing evidence highlighting the relevance of Bregs in promoting tumorigenic responses. Here we provide historical and emerging findings of the significance of Bregs in autoimmunity and transplantation, and how these insights have translated into the cancer field.