Tertiary lymphoid tissues (TLTs) are ectopic lymphoid tissues that develop in persistently inflammatory organs. Although studies have shown that TLTs occur in transplanted kidneys, the clinical significance of these TLTs was debatable. Using the histologic TLT development stages and the connection between TLTs and Banff pathologic scores, researchers investigated the implications of TLTs on future graft function for a study. They also investigated the risk factors for the emergence of TLTs. About 214 individuals who received living donor kidney transplants had serial protocol biopsy samples (0 hour, 1, 6, and 12 months) without rejection examined retrospectively. TLTs were classified as lymphocyte aggregates with indications of proliferation, with the lack (stage I) or presence (stage II) of follicular dendritic cells determining their stage. 

TLTs were found in just 4% of patients during the 0-hour biopsy. Prevalence climbed to over 50% at the 1-month biopsy, and then slightly more for the next 12 months. The proportion of advanced stage II TLTs steadily rose, reaching 19% at the 12-month biopsy. When compared to individuals with no TLTs or stage I TLTs, the presence of stage II TLTs was linked with a greater risk of renal function deterioration following transplantation. At 12 months, stage II TLTs were linked with more severe tubulitis and interstitial fibrosis/tubular atrophy, as well as worse graft performance regardless of the degree of interstitial inflammation. Rituximab pre transplantation therapy significantly reduced the formation of stage II TLTs.

TLTs were often discovered in clinically stable transplanted kidneys. TLTs in advanced stages II were linked with increasing graft malfunction that is unrelated to interstitial inflammation.