Identification of an IFN-γ-Producing Neutrophil Early in the Response to Listeria monocytogenes

Abstract

IFN-γ plays a critical role during the immune response to infection with Listeria monocytogenes. Early in the innate response NK cells are thought to be a primary source of IFN-γ; however, protection can be mediated by the presence of significant numbers of primed IFN-γ-secreting CD8+ T cells. In this report, we examined the early response to Listeria and found that 18 h after infection spleens contain CD11b+, Gr-1high, or Ly6G+ cells that produce significant IFN-γ. Morphological analysis of sorted Gr-1highIFN-γ+ and Gr-1lowIFN-γ+ or Ly6G+IFN-γ+ cells confirmed that these cells were neutrophils. The importance of IFN-γ production by these cells was further tested using adoptive transfer studies. Transfer of purified neutrophils from Ifng+/+ mice led to increased bacterial clearance in Ifng−/− mice. Transfer of Ifng−/− neutrophils provided no such protection. We conclude that neutrophils are an early source of IFN-γ during Listeria infection and are important in providing immune protection.