Hep to it ping.
This is really basic transplantation science that's very far away from clinical application in humans. I scanned the article for any mention of graft versus host disease and host versus graft disease. I found neither. Nor was there any mention of immunosuppression or immunosuppressants that I could find. Maybe they mentioned specific drugs that I missed.
PubMed gets 37 citations when queried about dipeptidyl peptidase IV-deficient F344 rats. The 30th citation was, "Suppression of arthritis by the inhibitors of dipeptidyl peptidase IV." From that you can surmise that dipeptidyl peptidase IV is involved in inflammation, at the least.