This product is a serum-free, animal-component-free B lymphocyte transformation medium with clearly defined ingredients. It is specifically optimized for the efficient activation, in vitro proliferation, and targeted induction of antibody secretion in human B cells. Its core formulation precisely mimics the activation microenvironment of the in vivo B cell immune synapse, integrating key stimulatory signals such as CpG ODN and CD40L with a unique combination of IL-4 and IL-21 cytokines. This combination powerfully drives the transformation of quiescent B cells into antibody-producing cells capable of secreting IgM/IgG, while significantly enhancing their proliferation efficiency, antibody titers, and somatic hypermutation levels. IL-21 cytokine combination. This formulation powerfully drives quiescent B cells to transform into antibody-producing cells secreting IgM/IgG, significantly enhancing proliferation efficiency, antibody titers, and somatic hypermutation levels. It ensures sustained clonal viability, phenotypic stability, and functional antibody secretion throughout the in vitro culture cycle, providing a reliable and stable foundation for vaccine immunogenicity evaluation, monoclonal antibody development, and immunological memory studies.