Multiparametric Optimization of Human Primary B‐Cell Cultures Using Design of Experiments

B cells are essential in the immune system, driving antibody production, cytokine secretion and antigen presentation. Studies in mouse models have illuminated key mechanisms underlying B-cell activation, differentiation, class-switch recombination and somatic hypermutation. However, the extent to which these findings translate to human biology remains unclear. To address this, we developed a human primary B-cell culture system using feeder cells engineered to express CD40L, supplemented with the cytokines BAFF, IL-4 and IL-21. Using a Design of Experiments (DOE) approach, we optimised critical parameters and dissected the individual contributions of each specific factor. Our results reveal that BAFF plays a negligible role, and IL-21 has more subtle effects, whereas CD40L and IL-4 are critical determinants of cell viability, proliferation and IgE class-switching. Furthermore, we find that engineered feeder cells can serve equally well as a source of cytokines, but providing these in purified form increases the flexibility of the system. This platform enables detailed investigation of human B-cell biology, offering insights into intrinsic and extrinsic regulators of antibody responses and providing a foundation for in vitro production of human primary antibodies.