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

ROMAGNOLI PA; PREMENKO-LANIER MF; LORIA GD; ALTMAN JD

Seattle, WA

Congreso; AAI IMMUNOLOGY 2009; 2009

The American Association of Immunologists, Inc.

Protection against intracellular pathogens is conferred by CD8 T cells, which require CD4T cell help to develop into effective memory CD8 T cells. It is believed thatCD4 help is provided via licensing of Antigen Presenting Cells (APCs) or IL-2secretion 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 thatCD11c+ 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 experiencedCD4 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 cells depending on the profile of the interacting CD4 T cell population.