Neutrophil regulation of immunotherapy for cancer is controlled by type II interferon.

Tumor resistance to immunotherapy is driven by several mechanisms, including those imposed by myeloid populations. Neutrophils are prominent within this landscape and display functional heterogeneity. Here, we investigated the contextual role of neutrophils, and using neutropenic mice, we found that the dominating function was to block the response when targeting T cells or myeloid cells. We found that neutrophils upregulated programmed death ligand-1 (PD-L1) in response to the treatment and, using this as a target, depleted this population. The upregulation of PD-L1 was dependent on interferon-γ (IFN-γ) produced by cytotoxic lymphocytes. Specific genetic deletion of cd274 or Ifngr1 on neutrophils showed that this was cell intrinsic. Moreover, in the absence of the capacity for specific IFN-γ-driven suppression, neutrophils changed their phenotype to support immunotherapy. Thus, we find that the type II interferon, IFN-γ, is key in determining whether neutrophils will support or block immunotherapy for cancer.