CLEC5A is a critical receptor in innate immunity against Listeria infection

The C-type lectin member 5A (CLEC5A) is a pattern recognition receptor for members of the Flavivirus family and has critical functions in response to dengue virus and Japanese encephalitis virus. Here we show that CLEC5A is involved in neutrophil extracellular trap formation and the production of reactive oxygen species and proinflammatory cytokines in response to Listeria monocytogenes. Inoculation of Clec5a ^-/- mice with L. monocytogenes causes rapid bacterial spreading, increased bacterial loads in the blood and liver, and severe liver necrosis. In these mice, IL-1β, IL-17A, and TNF expression is inhibited, CCL2 is induced, and large numbers of CD11b⁺Ly6C^hiCCR2^hiCX3CR1^low inflammatory monocytes infiltrate the liver. By day 5 of infection, these mice also have fewer IL-17A⁺ γδ T cells, severe liver necrosis and a higher chance of fatality. Thus, CLEC5A has a pivotal function in the activation of multiple aspects of innate immunity against bacterial invasion.The lectin receptor CLEC5A is a pattern recognition receptor that has been shown to detect dengue and Japanese encephalitis virus. Here the authors show that CLEC5A is needed for optimal ROS production, NET formation and other immune responses to Listeria monocytogenes in mice.