Interestingly, their lifespans would probably be affected very little.

> GzmK does not affect steady-state immune aging or aged immune responses after challenge

Virtually all old mice die of cancer, especially in the lab. If GzmK doesn't mitigate immune system aging, GzmK-null mice are still going to die of cancer, for little or no change in lifespan. (But presumably an improved healthspan due to reduced soft tissue and bone aging.)

I’d unironically love to have a pet rat that lives longer than a few years.

Can't wait for this to escape in New York City. Ageless undying sewer rats - what a utopia haha.