Complex Memory T-Cell Phenotypes Revealed by Coexpression of CD62L and CCR7

Abstract

Antigen-experienced T cells have been divided into CD62L ⁺ CCR7 ⁺ central memory (T _CM ) and CD62L ⁻ CCR7 ⁻ effector memory (T _EM ) cells. Here, we examined coexpression of CD62L and CCR7 in lymphocytic choriomeningitis virus-specific memory CD8 T cells from both lymphoid and nonlymphoid tissues. Three main points emerged: firstly, memory cells frequently expressed a mixed CD62L ⁻ CCR7 ⁺ phenotype that differed from the phenotypes of classical T _EM and T _CM cells; secondly, T _CM cells were not restricted to lymphoid organs but were also present in significant numbers in nonlymphoid tissues; and thirdly, a major shift from a T _CM to T _EM phenotype was found in memory cells that had been stimulated repetitively with antigen.