Why do different donor lots of the same primary cell type behave differently in culture?

Differences between donor lots are a normal and expected characteristic of primary cells and reflect their inherent biological variability.
Unlike immortalized cell lines, primary cells retain many donor-specific characteristics present in vivo. As a result, cells isolated from different donors may respond differently under identical culture conditions.
Several factors can contribute to donor-to-donor variability, including:
- Age, sex, health status, and lifestyle of the donor (for example smoking habits)
- Genetic differences that influence cell growth, metabolism, differentiation potential, and gene expression
- Variations in adaptation to in vitro culture conditions
- Cellular age and remaining replicative lifespan, as primary cells have a finite proliferative capacity and may enter senescence at different rates
As a consequence, researchers may observe differences between donor lots with respect to growth rate, morphology, differentiation capacity, and experimental responses. These differences are inherent to primary cell biology and do not necessarily indicate a quality issue.
For applications that require reduced biological variability, pooled donor cells may be a suitable alternative. By combining cells from multiple donors, pooled lots help average donor-specific effects and provide a biological response across a broader donor population.