New research has revealed that red blood cells function as critical immune sensors by binding cell-free DNA, called nucleic acid, present in the body’s circulation during sepsis and COVID-19, and that this DNA-binding capability triggers their removal from circulation, driving inflammation and anemia during severe illness and playing a much larger role in the immune system than previously thought. Scientists have long known that red blood cells, which are essential in delivering oxygen throughout the body, also interacted with the immune system, but didn’t know whether they directly altered inflammation, until now. The study, led by researchers at the Perelman School of Medicine at the University of Pennsylvania, was published today in Science Translational Medicine.