CD8 alpha alpha -Mediated Survival and Differentiation of CD8 Memory T Cell Precursors

Memory T cells are long-lived antigen-experienced T cells that are generally accepted to be direct descendants of proliferating primary effector cells. However, the factors that permit selective survival of these T cells are not well established. We show that homodimeric alpha chains of the CD8 molecule (CD8 alpha alpha ) are transiently induced on a selected subset of CD8 alpha beta super(+) T cells upon antigenic stimulation. These CD8 alpha alpha molecules promote the survival and differentiation of activated lymphocytes into memory CD8 T cells. Thus, memory precursors can be identified among primary effector cells and are selected for survival and differentiation by CD8 alpha alpha .