Functionally distinct LAG-3 and PD-1 subsets on activated and chronically stimulated CD8 T cells

Area of Science:

• Immunology
• Cellular Biology
• Molecular Biology

Background:

• Lymphocyte Activation Gene-3 (LAG-3) and Programmed Death 1 (PD-1) are immune checkpoint proteins that regulate T cell function.
• Both LAG-3 and PD-1 are transiently expressed on activated CD8 T cells but persist in tolerizing environments.
• Previous studies showed that blocking LAG-3 or PD-1 restores function in tolerized Ag-specific CD8 T cells.

Purpose of the Study:

• To determine if tolerized CD8 T cells coexpress PD-1 and LAG-3 or represent distinct functional populations.
• To characterize the phenotypic and functional differences between CD8 T cell populations defined by LAG-3 and PD-1 expression under tolerizing conditions.

Main Methods:

• Flow cytometry was used to analyze CD8 T cell populations based on LAG-3 and PD-1 expression.
• Phenotypic and functional assays were performed on identified CD8 T cell subsets.
• Mechanistic studies investigated the role of antigen concentration and inflammatory signals in LAG-3 and PD-1 expression.

Main Results:

• Three distinct CD8 T cell populations were identified under tolerizing conditions using LAG-3 and PD-1 staining.
• These populations exhibited unique phenotypic and functional characteristics.
• Antigen concentration and proinflammatory signals were found to control LAG-3 and PD-1 expression phenotypes on CD8 T cells.

Conclusions:

• Tolerized CD8 T cells can be classified into distinct subsets based on LAG-3 and PD-1 expression.
• Signaling through PD-1 and LAG-3 pathways has differential functional outcomes on CD8 T cells in tolerance.
• Modulating antigen and cytokine signaling can influence CD8 T cell tolerance via LAG-3 and PD-1 pathways.