Introduction: Several studies demonstrated that B cells can produce granzyme B (GZMB). The data on their function, however, is controversial and both regulatory and effector functions have been reported. Less is known about the frequency and phenotype of GZMB⁺ B cells in the breast tumor draining lymph nodes. 

Materials and methods: Mononuclear cells were isolated from 48 fresh breast tumor draining lymph nodes using Ficoll-Hypaque gradient centrifugation. Cells were stimulated in vitro with recombinant interleukin (IL)-21 and anti-BCR (B cell receptor) for 16 hours and Brefeldin were added to the culture in the last 6 hours. Cells were then stained with anti-CD19 and Granzyme B antibodies and subjected to flow cytometric analysis.

Results:  Our results revealed that 7.7±3.8% of B cells could produce GZMB with a non-significant declining trend in the metastatic lymph nodes. However, in patients with invasive ductal carcinoma of the breast (excluding patients whose tumors had medullary features), the percentage of GZMB producing B cells was significantly lower in the metastatic lymph nodes than in the non-metastatic nodes (P=0.01). Phenotypical analysis showed that GZMB⁺ B cells could have either CD24^low/-CD27^- (naïve) or CD24^hiCD27⁺ (active/memory) phenotype.

Conclusion: We could detect a subpopulation of B cells in the breast tumor draining lymph nodes capable of GZMB production. Further functional studies are needed to reveal their significance in the immunity against breast cancer.

Keywords: B cells, Granzyme B, breast Cancer