This news item from the Cornell Chronicle is about: Cornell researchers have discovered there is a division of labor among immune cells that fight invading pathogens in the body. The study, published June 14 in the journal Cell, finds for the first time that fetal immune cells are present in adults and have specialized roles during infection. In fact, the first immune cells made in early life are fast-acting first responders to microbes in adulthood. These immune cells – called CD8+ T cells – come in fetal and adult varieties, which originate in separate parts of the body and are hardwired with intrinsically different properties. The current paradigm is that, around the time of birth, the body switches from making and using fetal T cells to adult T cells to defend itself. But Cornell researchers used a unique study design to show that fetal T cells persist into adulthood and have different roles than adult cells in fighting infection.