Abundance of interstitial eosinophils in renal allografts is associated with vascular rejection.

BACKGROUND: The authors investigated the possible relevance of significant interstitial graft eosinophilic infiltrate (SIGEI) to the pathologic diagnosis of renal transplants.
METHODS: The authors performed a clinical and pathologic review of 29 consecutive patients with renal allograft failure and nephrectomy. As a result of their size, such specimens are more conducive than biopsies to the investigation of large blood vessels. SIGEI was diagnosed when eosinophils represented 10% or more of the interstitial inflammatory infiltrate. Vascular rejection was graded according to the Banff criteria. Risk for allergic interstitial nephritis and immunosuppression at the time of the nephrectomy-high dose, minimal, or none-was determined from the clinical history.
RESULTS: SIGEI was observed in 13 of the 29 patients and was absent in 16. Vascular (Banff type II) rejection was present in 11 of 13 cases with SIGEI and in 9 of 16 cases without SIGEI. The relation between SIGEI and Banff type II rejection was statistically significant: in 14 patients on high-dose immunosuppression, vascular rejection was present in all 5 cases with SIGEI, whereas in the 9 grafts without SIGEI, only 3 had vascular rejection (P=0.04). The authors did not find an association between SIGEI and risk for iatrogenic interstitial nephritis: SIGEI was seen in only 4 of 15 patients with high or moderate iatrogenic risk.
CONCLUSIONS: In this series of allograft nephrectomies, SIGEI was significantly associated with vascular rejection (Banff type II) but not with risk of allergic iatrogenic nephritis, suggesting that the presence of SIGEI may be a helpful criterion in the pathologic diagnosis of renal allografts.