The interplay between eosinophils and T-cells in breast cancer immunotherapy.

Treatment with immune checkpoint inhibitors (ICI) has revolutionized cancer management for multiple tumor types, including breast cancer. However, not all patients respond to ICI and unraveling the determinants and mechanisms of response still remains an unmet need. A recent study has uncovered the critical role of eosinophils in mediating immunotherapy effect in breast cancer, mainly by stimulating the activation of CD8+ T-cells. Furthermore, the intratumoral eosinophil recruitment was directed by CD4+ T-cells and the interleukins IL-5 and IL-33, thus providing the rationale for targeting eosinophils to enhance ICI response.