CD47(high) expression on CD4 effectors identifies functional long-lived memory T cell progenitors.

T cell memory is the hallmark of adaptive immunity. Central questions are to determine which cells among proliferating effector T cells will live beyond the crash of the immune response (IR) and develop into functional memory T cells. CD47, considered as a marker of self, is implicated in cell death, cell elimination, and in the inflammatory response. We report in this article that CD47 expression was transiently regulated on Ag-specific CD4 T cells, that is, from CD47(high) to CD47(low) to CD47(high), during the course of the in vivo IR. Specifically, CD47(high) status marked central memory CD4 T cell precursors at an early time point of the IR. By contrast, cytokine production was a functional attribute restricted to CD47(high), but not CD47(low), polyclonal effector CD4 T cells during recall responses in an experimental model of chronic airway inflammatory disease. Passive transfer of CD47(high), but not CD47(low), CD4 T cells in nonlymphopenic naive mice generated long-lived memory T cells capable of anamnestic responses. We conclude that CD47(high) status on CD4 T cells identifies functional long-lived memory T cell progenitors.