A major histocompatibility complex class I-dependent subset of memory phenotype CD8+ cells

Abstract

Most memory phenotype (MP) CD44hi CD8+ cells are resting interleukin (IL)-15-dependent cells characterized by high expression of the IL-2/IL-15 receptor β (CD122). However, some MP CD8+ cells have a CD122lo phenotype and are IL-15 independent. Here, evidence is presented that the CD122lo subset of MP CD8+ cells is controlled largely by major histocompatibility complex (MHC) class I molecules. Many of these cells display surface markers typical of recently activated T cells (CD62Llo, CD69hi, CD43hi, and CD127 lo) and show a high rate of background proliferation. Cells with this phenotype are highly enriched in common γ chain-deficient mice and absent from MHC-I-/- mice. Unlike CD122hi CD8+ cells, CD122lo MP CD8+ cells survive poorly after transfer to MHC-I-/- hosts and cease to proliferate. Although distinctly different from typical antigen-specific memory cells, CD122lo MP CD8+ cells closely resemble the antigen-dependent memory CD8 + cells found in chronic viral infections. JEM © The Rockefeller University Press.