Macrophage Migration Inhibitory Factor Is Detrimental in Pneumococcal Pneumonia and a Target for Therapeutic Immunomodulation.

Mortality from pneumococcal pneumonia remains high despite antibiotic therapy, highlighting the pathogenic potential for host inflammation. We demonstrate that macrophage migration inhibitory factor (MIF), an innate immune mediator, is detrimental for survival and associated with lung pathology, inflammatory cellular infiltration, and bacterial replication in a mouse model of pneumococcal pneumonia, despite being necessary for clearance from the nasopharynx. Treatment of animals with a small-molecule inhibitor of MIF improves survival by reducing inflammation and improving bacterial control. Our work demonstrates that MIF modulates beneficial versus detrimental inflammatory responses in the host-pneumococcal interaction and is a potential target for therapeutic modulation.