Influenza-activated alveolar macrophages protect against death by malaria-associated acute lung injury (MA-ALI) during coinfection

Here we show that malaria-influenza coinfection does not yield worse prognosis in mice. Rather, coinfection with Influenza/A/X31 protects mice from severe malaria-associated acute lung injury (MA-ALI).

This effect arises from differences in CD8-mediated pathology, rather than a failure by Plasmodium parasites to establish infection, and it depends on an active influenza infection in the lung. Surprisingly, recruitment of Plasmodium-reactive CD8 T cells to the lung was unaffected by influenza coinfection. Rather, an influenza-induced expansion of Arginase 1 (Arg1)-expressing alveolar macrophages suppressed the cytotoxic capabilities of pathogenic CD8 T cells once they had been recruited to the lung, rendering them harmless.