Cytokine-Mediated Programmed Proliferation of Virus-Specific CD8+ Memory T Cells

Abstract

During infection, CD8(+) Tcells not only respond to antigenic signals through their Tcell receptor (TCR) but also incorporate inflammatory signals from cytokines produced in the local infected microenvironment. Transient TCR-mediated stimulation will result in programmed proliferation that continues despite removal of the antigenic stimulus, but it remains unclear whether brief exposure to specific cytokines will elicit similar effects. Here, we have demonstrated that brief stimulation of memory Tcells with interleukin-12 (IL-12) and interleukin-18 (IL-18) results in tightly regulated programmed proliferation, in addition to acquisition of enhanced virus-specific cytokine production and cytolytic activity. CD8(+) Tcells briefly exposed to IL-12 and IL-18 invitro showed improved antiviral activity invivo, as demonstrated by increased proliferation and reduced viremia. These results indicate that even transitory exposure to inflammatory cytokines can provide a selective advantage to infiltrating CD8(+) Tcells by triggering a developmental program that is initiated prior to direct contact with virus-infected cells.