The balance of regulatory and stimulatory B cell subsets in breast cancer draining lymph nodes correlates with tumor prognostic factors

Aims: B cells can promote or inhibit immune responses against breast cancer. We investigated changes in the frequency of B cells with stimulatory or regulatory capacity in breast tumor draining lymph nodes during cancer progression. Main methods: We isolated mononuclear cells from fresh axillary lymph nodes (LNs) of 44 patients with breast cancer and stained lymphocytes with antibodies against CD19, CD80, CD86, CD39 and CD73. To assess programmed death-1 (PD-1) and PD-ligand 1 (PD-L1) expression, lymphocytes were briefly stimulated, stained for CD19, PD-1 and PD-L1, and examined with flow cytometry. Key findings: The frequency of CD80(+) B cells was higher in nonmetastatic lymph nodes, while the percentage of CD86(+) B cells showed a positive relationship with higher tumor grade and higher numbers of involved LNs. A small proportion of unstimulated B cells expressed PD-1 or PD-L1 but these molecules were rapidly upregulated on B cells following activation. The frequency of stimulated PD-L1(+) B cells showed an inverse association with estrogen and progesterone receptor expression and a nonsignificant positive association with tumor grade. In addition, the percentage of unstimulated PD-1(+) B cells was higher in patients with higher-grade tumors. CD73 expression on B cells was associated with lower numbers of involved LNs, and the frequency of CD39+ B cells was higher in patients with larger tumors. Significance: CD86(+), CD39(+), PD-1(+) and PD-L1(+) B cells showed associations with poor prognostic factors, therefore their potential role in the suppression of the immune responses against breast cancer should be evaluated in greater detail.