A reporter mouse model to map RIG-I expression and function in vivo

RIG-ImScar reporter mice enable fluorescence imaging and immunoprecipitation of RIG-I, revealing strong RIG-I enrichment in circulatory, lymphoid, and mucosal tissues.

• Why it matters: Tools to track RIG-I in vivo are limited, making it hard to map where RIG-I is expressed and which immune cells sense RNA virus–like signals.
• What they did: The team engineered RIG-ImScar for fluorescence imaging and tractable immunoprecipitation, then crossed it with Mx1GFP to separate steady-state sentinel cells from IFN-responder cells. They blocked IFNAR with a monoclonal antibody and used intranasal SLR14 to test lung responses.
• The result: RIG-I is upregulated by IFN, basal expression is largely type I IFN–independent except in Ly6Chi monocytes, and lung mapping after SLR14 identifies alveolar macrophages as a key RIG-I sensor cell population. Depleting alveolar macrophages, but not neutrophils, slightly impaired lung IFN responses.

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