I once read that there's something somewhat unique about the immune system of bats (very permissive?) that allows viruses to live in bats relatively undisturbed

I once read that there's something somewhat unique about the immune system of bats (very permissive?) that allows viruses to live in bats relatively undisturbed, allowing them a lot of time to mutate and thrive without affecting the bats much. Edit: "Several studies have indicated that bats have unique defense mechanisms that allow them to be persistently or latently infected with viruses. Factors leading to an increase in the viral load of persistently infected bats would facilitate shedding of virus." Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6410205/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6410205/