Predictors of Anti-Thymocyte Globulin Treatment for T-Cell Mediated Rejection in Liver Transplantation: A Retrospective Study

T-cell mediated rejection (TCMR) remains a common complication following liver transplantation. Rabbit Anti-Thymocyte Globulin (rATG) is generally reserved for severe or steroid-refractory rejection; however, predictors associated with its use remain poorly characterized. This single-center retrospective study included adult deceased donor liver transplant recipients with biopsy-proven TCMR (Rejection Activity Index [RAI] ≥ 3) between September 2022 and September 2024. Univariable and multivariable Firth penalized logistic regression analyses were performed. A total of 182 TCMR episodes occurring among 151 recipients were included, of which 23 (12.6%) received rATG. Episodes treated with rATG had higher median ATL, AST, bilirubin, and RAI scores at index biopsy. In multivariable analysis, increasing RAI score was independently associated with rATG utilization (adjusted OR 2.13 per one-point increase, p<0.001). Late-onset rejection, biliary complications, age, prior rejection, and induction regimen were not significantly associated with rATG use. Overall infection rates at one year were similar between groups, although cytomegalovirus viremia and bacteremia were more frequent in rATG-treated patients. These findings suggest that, in clinical practice, histologic severity is a dominant driver of escalation to lymphocyte-depleting therapy. Histologic improvement was observed following rATG therapy with similar overall infection rates, though higher occurrences of bacteremia. These findings may guide earlier recognition and escalation of therapy in high-risk TCMR, though additional studies are needed to assess long-term graft outcomes.