Since the initial cell populations are obtained from the patients themselves in autologous cell therapies, they can be highly hetero­geneous as the quality of the cells depends on the patient’s health. This can reduce the reproducibility and definition of the final prod­uct [24]. With a limited amount of starting material available from the patient, the amount of material available for quality control test methods may be correspondingly limited. Thus, the sampling strate­gies to ensure a sucient final product dose for patients may in turn aect the accuracy of the test results which reflects the properties of a batch of CTGTP [48]. Several cell types are also adherent in nature, requiring detachment from cultures in their intact form before being processed down- stream, thus potentially aecting cell quality [3]. Furthermore, cells are highly sensitive to their environment and dis­play changing behaviours in response, further contributing to their variability [51]. Patients receiving the therapy are also cancer patients who undergo aggressive therapies which can aect T-cell fitness nega­tively, leading to failure in product generation altogether [52].