Thymic OX40 expression discriminates cells undergoing strong responses to selection ligands

Area of Science:

• Immunology
• T cell biology
• Thymic selection

Background:

• OX40 (tumor necrosis factor receptor superfamily member 18) is a receptor primarily found on activated and regulatory T (Treg) cells.
• Its expression pattern suggests a potential role beyond activated T cells.

Purpose of the Study:

• To investigate the expression of OX40 on naive T cells within the thymus.
• To determine if OX40 expression in the thymus is linked to specific T cell populations or signaling events.

Main Methods:

• Utilized an Ox40-cre allele for lineage tracing in thymocytes.
• Analyzed OX40 expression in conjunction with T cell markers like CD25.
• Correlated OX40 expression with thymic positive selection signaling strength.

Main Results:

• A subpopulation of naive T cells was identified to have previously expressed OX40 in the thymus.
• Thymic OX40 expression was observed in CD25(high) regulatory T (Treg) cell precursors.
• Previous OX40 expression on naive T cells correlated with a partially activated phenotype, distinct from other naive T cells.
• Thymic OX40 expression marked thymocytes that received strong positive selection signals.

Conclusions:

• The findings suggest that thymic OX40 expression identifies T cells, including Treg precursors and a distinct naive T cell subset, selected through robust signaling.
• This highlights a role for strong thymic self-ligand interactions in shaping specific T cell populations.