Figure 1.

A model depicting the proposed roles of IFN-I and neutrophils during F. tularensis infection is shown. Pulmonary infection with F. tularensis triggers IFN-I production from innate immune cells such as alveolar macrophages. IFN-I may sensitize F. tularensis-infected neutrophils for cell death and contribute to an overall reduction in neutrophil numbers at the site of infection. IFN-I may also directly limit neutrophil recruitment via inhibition of IL-17 producing γδT cells or suppression of other neutrophil chemoattractants. Suppression of neutrophil recruitment may prevent tissue damage associated with excessive infiltration of neutrophils as well as lead to inadequate bacterial clearance, resulting in an unfavorable outcome. An optimal neutrophil response may require moderate recruitment at an early time point to aid in prompt clearance of bacteria without causing significant inflammation later during pulmonary tularemia.