Complex memory T-cell phenotypes revealed by coexpression of CD62L and CCR7

Area of Science:

• Immunology
• T cell biology
• Virology

Background:

• Antigen-experienced T cells differentiate into central memory (TCM) and effector memory (TEM) subsets.
• TCM cells are characterized by CD62L+ CCR7+ expression, while TEM cells express CD62L- CCR7-.
• Understanding memory T cell heterogeneity is crucial for vaccine and immunotherapy development.

Purpose of the Study:

• To investigate the coexpression of CD62L and CCR7 in lymphocytic choriomeningitis virus (LCMV)-specific memory CD8 T cells.
• To determine the distribution of memory T cell subsets in both lymphoid and nonlymphoid tissues.
• To analyze phenotypic changes in memory T cells upon repetitive antigen stimulation.

Main Methods:

• Flow cytometry analysis of CD8 T cells from lymphoid and nonlymphoid tissues.
• Characterization of memory T cell phenotypes based on CD62L and CCR7 expression.
• In vivo studies involving LCMV infection and antigen re-exposure.

Main Results:

• A novel CD62L- CCR7+ memory T cell phenotype was frequently observed, distinct from classical TCM and TEM cells.
• Central memory T cells (TCM) were found in significant numbers within nonlymphoid tissues, not solely confined to lymphoid organs.
• Repetitive antigen stimulation induced a notable shift in memory T cell phenotype from TCM towards TEM.

Conclusions:

• Memory CD8 T cell populations display greater phenotypic diversity than previously defined.
• Central memory T cells possess the capacity for tissue-resident function beyond lymphoid compartments.
• Dynamic phenotypic plasticity of memory T cells is influenced by the antigen exposure context.