Peripheral tissues reprogram CD8+ T cells for pathogenicity during graft-versus-host disease.

Area of Science:

• Immunology
• Transplantation Biology
• Systems Biology

Background:

• Graft-versus-host disease (GVHD) is a major complication of allogeneic stem cell transplantation.
• Current GVHD treatments target all T cells systemically, but the mechanisms driving T cell pathogenicity are not fully understood.

Purpose of the Study:

• To create a spatial map of effector T cell (TE) differentiation during GVHD.
• To identify the factors that program TE to become pathogenic in specific tissues.

Main Methods:

• Weighted gene coexpression network analysis (WGCNA) was used to map TE differentiation.
• Differential gene expression analysis was performed in specific tissues.
• The role of Langerhans cells and Notch signaling in skin GVHD was investigated.

Main Results:

• Effector T cell programming varies significantly by tissue location in both mice and humans.
• Tissue-autonomous mechanisms, not T cell receptor repertoire or initial activation status, reprogram TE.
• In the skin, Langerhans cells provide Notch-dependent signals that induce pathogenic TE programs.

Conclusions:

• The target organ's environment is the primary driver of T cell pathogenicity in GVHD.
• Future GVHD therapies should focus on organ-specific interventions to mitigate immunopathology.
• Avoiding global immunosuppression is crucial while targeting specific pathogenic pathways.