RIPK1 and viral infectious disease: Indeed, consistent with the cell viability assay, RIPK1 co-immunoprecipitated with ZBP1 and RIPK3 in necroptosis-susceptible cells (HT29 WT, mutZα1, and mutRHIMB) following viral infection but was not in cells with inactivating mutations in Zα2 or RHIM A (mutZα2, mutZα1Zα2, and mutRHIMA) (Fig 5C).