The success of allogeneic cell therapies depends on high-quality starting material derived from healthy donors. However, variability in donor characteristics and collection procedures such as leukapheresis can impact cell yield and product quality. The aim of this study was to identify donor‑ and procedure‑related factors associated with leukopak yield and composition, and to assess the stability of immune‑cell subsets in repeat donors.

This was a retrospective analysis of 184 leukopak donations from 104 healthy donors across three German centers (2021–2024). Donor demographics, pre-collection complete blood count (CBC) values, and leukapheresis parameters were evaluated to identify predictors of white blood cell (WBC) yield and leukopak composition. Intra-donor variability was assessed in repeat donors.

Donors were predominantly male (96.2%) with a mean age of 36 years and body mass index (BMI) of 30.0 kg/m². The average WBC yield per leukopak was 15.9 × 10⁹ cells, with high viability (99.1%). WBC yield showed positive correlations with BMI (r = 0.2751, p = 0.0001), processed blood volume (r = 0.2673, p = 0.0002), and pre-collection CBC values (r = 0.3939, p < 0.0001). Natural killer cell frequency increased significantly with age, while CD3+ T cells declined (both p < 0.0001). Repeat donors demonstrated consistent immune cell profiles over time, despite some variability in total WBC yield.

This study identified key donor characteristics that influence leukopak collection efficiency, particularly BMI, age, and pre-collection CBC values. Understanding these demographic factors enables better management of leukopak variability, leading to more predictable, consistent, and efficient starting materials for cell therapy manufacturing.