Increased B Regulatory Phenotype in Non-Metastatic Lymph Nodes of Node-Positive Breast Cancer Patients

Tumour-draining lymph nodes (TDLNs) are centre in orchestrating the immune responses against cancer. The cellularity and lymphocyte subpopulations change in the process of cancer progression and lymph node involvement. B lymphocyte subsets and their function in breast cancer-draining lymph nodes have not been well elucidated. Here, we studied the influence of tumour metastasis on the frequencies of different B cell subsets including naïve and memory B cells as well as those which are known to be enriched in the regulatory pool in TDLNs of 30 patients with breast cancer. Lymphocytes were obtained from a fresh piece of each lymph node and stained for CD19 and other B cell-associated markers and subjected to flow cytometry. Our investigation revealed that metastatic TDLN showed a significant decrease in active, memory and class-switched B cells while the frequencies of B cells with regulatory phenotypes were not changed. However, CD27(hi) CD25(+) and CD1d(hi) CD5(+) B regulatory subsets significantly increased in non-metastatic lymph nodes (nMLNs) of node-positive patients compared with node-negative patients. Our data provided evidence that in breast cancer, metastasis of tumour to axillary lymph nodes altered B cell populations in favour of resting, inactive and unswitched phenotypes. We assume that the lymphatic involvement may cause an increase in a subset of regulatory B cells in non-metastatic lymph nodes.