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/μL (IQR 9-43/μL) vs. 10/μL (IQR 4-19/μL), p = 0.050) and higher PLT on day 7 (143 × 10/μL (IQR 103-168 × 10/μL) vs. 105 × 10/μL (IQR 68-141 × 10/μL), p = 0.02), with higher ALC on day 14 (308/μL (IQR 171-530/μL) vs. 180/μL (IQR 93-317/μL), p = 0.016) and on day 21 (529/μL (IQR 240-610/μL) vs. 225/μL (IQR 121-328/μL), 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.