Tumor-associated neutrophils drive B-cell recruitment and their differentiation to plasma cells.

A major mechanism through which neutrophils have been suggested to modulate tumor progression involves the interaction and subsequent modulation of other infiltrating immune cells. B cells have been found to infiltrate various cancer types and play a role in tumor immunity, offering new immunotherapy opportunities. Nevertheless, the specific impact of tumor-associated neutrophils (TANs) on B cells has largely been overlooked. In the current study, we aimed to characterize TANs' role in the recruitment and modulation of B cells in the tumor microenvironment (TME). We showed that TANs actively participate in the recruitment of B cells to the TME and identified TNFα as the major cytokine mediating B-cell chemotaxis by TANs. The recruitment of CD45+B220+CD138- splenic B cells by TANs in vitro resulted in B-cell phenotypic modulation, with 68.6{plus minus}2.1% of the total migrated B cells displaying a CD45-B220+CD138+ phenotype, typical for plasma cells. This phenotype mirrored the large proportion (54.0{plus minus}6.1%) of CD45-B220+CD138+ intratumoral B cells (i.e., plasma cells) in LLC tumors. We next confirmed that the differentiation of CD45+B220+CD138- B cells to functionally active CD45-B220+CD138+ plasma cells required contact with TANs, was independent of T cells, and resulted in IgG production. We further identified membranal BAFF on TANs as a potential contact mechanism mediating B-cell differentiation, as blocking BAFF-R significantly reduced by 20% IgG production. Our study, therefore, demonstrates that TANs drive the recruitment and modulation of B cells into plasma cells in the TME, hence opening new avenues in the targeting of the immune system in cancer.