Practical Issues and Future Perspectives for Inflammation in Areas of Interstitial Fibrosis and Tubular Atrophy in Chronic Active T cell-Mediated Rejection: Three Case Reports with Commentary.

The 2017 Banff meeting provided specific criteria for the diagnosis of tubulointerstitial changes in chronic active T cell-mediated rejection (CATCR), with an emphasis on inflammation in areas of interstitial fibrosis and tubular atrophy, which was thought to reflect an ongoing T cell-mediated alloimmunity. CATCR is considered to occur as a consequence of persistent or recurrent acute T cell-mediated rejection. Acute T cell-mediated rejection is an acute cytotoxic T-cell reaction to HLA antigens on the donor kidneys and causes tubulitis, interstitial inflammation, and intimal arteries. However, unlike early T-cell transplant damage, CATCR can sometimes be difficult to diagnose because the subsequent chronic T-cell damage can become more complex from the accumulation of previous immune and nonimmune injuries. Furthermore, scoring inflammation in areas of interstitial fibrosis and tubular atrophy has potential problems because other diseases and not even native kidneys can have scattered inflammatory cells. Therefore, detailed insights on the pathogenesis of CATCR are indispensable for appropriate diagnosis and further treatment. In this study, the pathologic characteristics and possible factors involved in the interstitial lesions in both typical and complex cases of CATCR are discussed.