Cutting edge: Increased expression of Bcl-2 in antigen-specific memory CD8(+) T cells

Bcl-2 plays a critical role in regulating cell survival and apoptosis, We e xamined Bcl-2 expression in virus-specific CD8 T cells during the expansion , death, and memory phases of the T cell response following infection of mi ce with lymphocytic choriomeningitis virus (LCMV), Naive CD8 T cells expres sed a basal level of Bcl-2 that was down-regulated in effector CD8 T cells just before the death phase, Bcl-2 levels remained low during the death pha se but surviving memory CD8 T cells expressed higher levels of Bcl-2 than n aive cells. These changes were shown to occur in LCMV TCR transgenic cells as well as virus-specific CD8 T cells in C57BL/6 and BALB/c mice identified by MHC class I tetramers, In all instances, memory CD8 T cells expressed h igher levels of Bcl-2, suggesting that increased Bcl-2 expression plays a r ole in the long-term maintenance of memory CD8 T cells in vivo.