Cutting edge: Antigen-independent CD8 T cell proliferation

Recent analyses of CD8 T cell responses to Listeria monocytogenes infection demonstrate that the duration of in vivo T cell proliferation is not deter mined by the amount or duration of Ag presentation. However, the extent to which T lymphocytes are capable of proliferating in the absence of Ag is un known. Herein we demonstrate that CD8 T lymphocytes undergo up to eight rou nds of proliferation in the absence of Ag following transient, 2.5-h in vit ro antigenic stimulation. Ag-independent expansion of CD8 T cells is driven by IL-2 and is further augmented by IL-7 or IL-15. These experiments clear ly demonstrate that CD8 T cells undergo prolonged proliferation following t ransient Ag exposure and support the notion that in vivo CD8 T cell expansi on following infection can be uncoupled from Ag presentation.