IFN-gamma receptor signaling regulates memory CD8+ T cell differentiation

Area of Science:

• Immunology
• T cell biology
• Innate and adaptive immunity

Background:

• Interferon-gamma (IFN-gamma) is crucial for immune regulation, but its role in CD8(+) T cell homeostasis is not fully understood.
• While IFN-gamma's antimicrobial functions are known, its precise mechanisms in controlling CD8(+) T cell populations require further investigation.

Purpose of the Study:

• To elucidate the distinct roles of host versus CD8(+) T cell-intrinsic IFN-gamma receptor (IFN-gammaR) signaling in CD8(+) T cell responses.
• To investigate how IFN-gammaR signaling influences T cell expansion, contraction, memory differentiation, and fate decisions under various conditions.

Main Methods:

• Adoptive T cell transfer experiments in mouse models.
• Utilizing peptide vaccination and lymphopenic conditions to study CD8(+) T cell dynamics.
• Analysis of T cell expansion, contraction, memory differentiation, and fate decisions.

Main Results:

• IFN-gammaR signaling within CD8(+) T cells is not essential for their expansion, contraction, or memory differentiation during peptide vaccination.
• Host IFN-gammaR signaling counterregulates CD8(+) T cell responses and effector memory generation, partly mediated by CD11b(+) cells.
• Host IFN-gammaR signaling limits naive CD8(+) T cell expansion and effector memory differentiation in lymphopenic mice.
• IFN-gammaR signaling in CD8(+) T cells influences memory fate decisions in lymphopenia, an effect reversed by high-affinity ligands.
• Host IFN-gammaR signaling controls the magnitude of CD8(+) T cell responses and memory differentiation in both lymphopenic and nonlymphopenic settings.

Conclusions:

• Host IFN-gammaR signaling acts as a brake on CD8(+) T cell responses and memory formation.
• IFN-gammaR signaling within CD8(+) T cells is critical for determining memory cell fate, particularly in response to weak T cell receptor ligands.
• These findings highlight a dual role for IFN-gammaR signaling in shaping adaptive immunity.