Lower basophil count after anti-thymocyte globulin induction is associated with lower incidence of acute cellular rejection in heart transplant recipients

Introduction: While lymphodepletion is considered a therapeutic effect of rabbit anti-thymocyte globulin (rATG), a concomitant decrease in basophil count (BC) has unknown clinical effect. Objective: To investigate the association between BC following rATG induction and acute cellular rejection (ACR) during the first post-HTx year. Methods: Retrospective single-center study included 183 HTx recipients receiving rATG induction between 2010 and 2021 (mean age 52 +/- 13 years, 23 % female). Absolute lymphocyte count (ALC), platelet (PLT) count and BC were assessed on days 0, 7, 14, and 21 following HTx. The primary outcome was the first ACR (grade >= 1B) within the first post-HTx year. Results: Patients with ACR had significantly higher BC on day 14 (17/mu L (IQR 9-43/mu L) vs. 10/mu L (IQR 4-19/mu L), p = 0.050) and higher PLT on day 7 (143 x 10(3)/mu L (IQR 103-168 x 10(3)/mu L) vs. 105 x 10(3)/mu L (IQR 68-141 x 10(3)/mu L), p = 0.02), with higher ALC on day 14 (308/mu L (IQR 171-530/mu L) vs. 180/mu L (IQR 93-317/mu L), p = 0.016) and on day 21 (529/mu L (IQR 240-610/mu L) vs. 225/mu L (IQR 121-328/mu L), p < 0.001). In univariate analysis, ACR was associated with higher BC on day 14 (p = 0.004), higher PLT on day 7 (p = 0.02), higher ALC on days 14 (p = 0.04) and 21 (p < 0.001). Multivariable regression model showed the most significant association between higher BC on day 14 and ACR (p = 0.015). Conclusion: Lower BC two weeks after rATG induction is associated with less ACR during the first post-HTx year.