Expression of the Transcription Factor FOXP3 in Human Peripheral Blood B-Cell Subtypes (CD19+CD39+ and CD19+CD39-) and Evaluation of Their Regulatory Function

The aim of this study was to evaluate FOXP3 expression in CD19⁺CD39⁺ and CD19⁺CD39⁻ B cells, and to investigate its potential regulatory role. Peripheral B cells were obtained from 25 volunteers. FOXP3 expression at the mRNA and protein levels was analyzed in CD19⁺CD39⁺ and CD19⁺CD39⁻ B cells by FACS and RT-qPCR. Suppressive activity was assessed through co-cultures of PBMC with CD19⁺CD39⁺ and CD19⁺CD39⁻ B cells stimulated with anti-CD3/CD28, evaluating T cell proliferation and the percentage of Th1 cells. The percentage of CD19⁺CD39⁺ FOXP3⁺ B cells was higher compared to other phenotypes. There was a positive correlation between FOXP3 and CD39 in CD19⁺ B cells. FOXP3 mRNA was increased in CD19⁺CD39⁺ B cells compared to CD19⁺CD39⁻ B cells. CD19⁺CD39⁻ B cells reduced the proliferation, the percentage of Th1 cells, and expressed higher IL-10 mRNA compared to CD19⁺CD39⁺ B cells. B cell phenotypes were inversely associated with Th1 cells and CRP. CD19⁺CD39⁻ was associated with HOMA-β. CD19⁺CD39⁺ was inversely associated with HbA1c. FOXP3 is expressed on both CD19⁺CD39⁻ and CD19⁺CD39⁺ B lymphocytes. CD19⁺CD39⁻ cells showed high levels of IL-10 and low levels of FOXP3 mRNA. CD19⁺CD39⁻ B cells decreased the Th1 cells and were associated with β-cell function.