L-selectin-negative CCR7- effector and memory CD8+ T cells enter reactive lymph nodes and kill dendritic cells

Area of Science:

• Immunology
• Cell Biology
• T cell trafficking

Background:

• T lymphocytes typically require L-selectin and CCR7 for lymph node homing.
• Steady-state lymph node entry for T cells is restricted without these homing receptors.

Purpose of the Study:

• To investigate the recruitment of T cells lacking L-selectin and CCR7 to lymph nodes.
• To understand the mechanisms and functional consequences of this recruitment in reactive lymph nodes.

Main Methods:

• Analysis of T cell populations in draining lymph nodes after dendritic cell or adjuvant inoculation.
• Assessment of T cell recruitment via high endothelial venules.
• Evaluation of T cell interactions with dendritic cells and subsequent immune modulation.

Main Results:

• L-selectin-negative, CCR7-negative effector and memory CD8+ T cells were recruited to reactive lymph nodes.
• Recruitment was dependent on CXCR3 expression on T cells and CXCL9 expression in lymph nodes.
• Recruited T cells interacted with and eliminated antigen-bearing dendritic cells, suppressing naive T cell activation.

Conclusions:

• Inducible recruitment of blood-borne effector/memory T cells to lymph nodes is a novel mechanism.
• This process, mediated by CXCR3/CXCL9, can terminate primary immune responses.
• It also plays a role in limiting secondary immune responses by controlling antigen-presenting cells.