IFNγ binding to extracellular matrix prevents fatal systemic toxicity.

Area of Science:

• Immunology
• Molecular Biology
• Biochemistry

Background:

• Interferon-γ (IFNγ) is crucial for cellular immunity but high systemic levels cause immunopathology.
• IFNγ's C-terminal ECM-binding domain (EBD), composed of four amino acids (KRKR), mediates extracellular matrix interaction.
• The EBD is highly conserved across species, indicating a critical, yet understudied, function.

Purpose of the Study:

• To investigate the role of the IFNγ EBD in regulating cytokine bioavailability and systemic toxicity.
• To determine if ECM binding by IFNγ is essential for its bioactivity and immune function.
• To elucidate the protective mechanism conferred by local IFNγ retention.

Main Methods:

• Generated IFNγ lacking the EBD (IFNγ^ΔKRKR) using CRISPR-Cas9 gene editing.
• Assessed ECM binding, IFNγ receptor (IFNγR) interaction, and bioactivity of wild-type versus mutant IFNγ.
• Studied the effects of IFNγ^ΔKRKR overexpression in tumors and during lymphocytic choriomeningitis virus infection in mice.

Main Results:

• IFNγ^ΔKRKR retained IFNγR binding and bioactivity but lacked ECM binding.
• Tumor overexpression of IFNγ^ΔKRKR led to reduced local ECM binding, elevated systemic levels, and induced toxicity.
• IFNγ^ΔKRKR mice exhibited higher systemic cytokine levels, exacerbated sickness behavior, weight loss, and fatal toxicity upon viral infection.

Conclusions:

• Local retention of IFNγ via its EBD is a critical mechanism for preventing systemic toxicity.
• The EBD regulates IFNγ bioavailability, mitigating adverse effects during sustained immune responses.
• Targeting the IFNγ EBD could offer therapeutic strategies for managing immune-mediated pathologies.