Direct CD8:CD4 T cell interactions improve memory recall of CD8 T cells (33.9)

TL;DRAbstract

Abstract Protection against intracellular pathogens is conferred by CD8 T cells, which require CD4 T cell help to develop into effective memory CD8 T cells. It is believed that CD4 help is provided via licensing of APCs or IL-2 secretion to optimally stimulate CD8 T cells. We propose a new model where T:T interactions also play a role in CD8 T cell memory formation. Here, we show that endogenous CD8 T cells, detected by tetramer enrichment, can acquire MHC class II when responding to infection. Next, we demonstrate that CD11c+ APCs are the main source of this MHC class II. Finally, we show that MHC class II bearing activated CD8 T cells can directly interact with experienced CD4 T cells impacting memory recall responses of CD8 T cells in vivo. These observations suggest that program differentiation of memory CD8 T cells involves a novel direct interaction between CD8 and CD4 T cells. Furthermore, this model may also facilitate the understanding of immune regulation exerted on CD8 T cel

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