Usually rats and mice are used for initial studies because they are inexpensive. These studies are then confirmed in a non rodent animal model (usually dogs), then in non-human primates, then tested in humans.
Only if the treatment is found to be efficacious in rodents will it usually be moved on to NH-primates and then humans.
The CD proteins are likely to be very similar between all these species, so the molecular interactions should be similar enough to maintain efficacy.
In Type I diabetes studies, at least, mouse results are notorious for not carrying over well into humans.
Given that Type I diabetes and the inflammation response reported here are both autoimmune responses, I have a strong suspicion that the results reported here will similarly not carry over well to humans.
Wouldn't some small non human primates be a better choice than dogs? Possibly cheaper too. Although since they are not generally native to the areas where researchers are likely to be, transportation costs might figure in. But, OTOH, they seem to do well in captivity, so they could be raised just for these purposes, just like mice and rats are.
Honestly, I think it has less to do with cost than it has to do with the short reproductive maturity cycle in rodents, coupled with the short gestation periods. It is possible to observe many generations, within several years vs. several decades, or several lifetimes...