Assessment of the duration of lymphocyte depletion after anti-thymocyte globulin for rejection in lung transplant recipients

Optimal strategies to detect response to rejection treatment with anti-thymocyte globulin (ATG) in lung transplant recipients (LTR) are poorly defined. We hypothesized that LTR with stable or improving lung function after ATG ["functional responders" (FR)] would have longer lymphocyte suppression than "non-responders" (NR). We present a case series of 22 FR and 11 NR who received ATG for rejection. FR had stabilization or increase in forced expiratory volume in 1-second at 6 months post-ATG. Multivariable proportional hazards regression demonstrated that, after adjusting for the effects of baseline absolute lymphocyte count and ATG dose, FR had reduced likelihood of lymphocyte normalization compared to NR (AHR: 0.017; 95%CI: 0.001-0.295). LTRs receiving ≥4.5mg/kg ATG had nearly longer time to normalization of absolute lymphocytes (p=0.052) and CD4 cells (p=0.021). In this case series, FR may have prolonged time to lymphocyte normalization, with LTRs receiving ≥4.5mg/kg ATG having significantly longer time until CD4 normalization.