A multimerized form of recombinant human CD40 ligand supports long-term activation and proliferation of B cells

Background aims: CD40-activated B cells have long been studied as potent antigen-presenting cells that can potentially be used for cancer immunotherapy. Nevertheless, their use in human clinical trials has been limited by the lack of a Good Manufacturing Practice-grade soluble human CD40 ligand that is able to induce activation and proliferation of primary B cells. We describe an in vitro method to effectively generate and expand B cells through the use of a multimerized form of human recombinant CD40 ligand (rCD40L).

Methods: Human B cells were isolated from healthy donors and cultivated with either rCD40L or on a monolayer of murine NIH3T3 cells stably expressing human CD40L (NIH3T3/tCD40L) as a widely used standard method. Morphology, expansion rate, immune phenotype and antigen presentation function were assessed.

Results: B cells efficiently proliferated in response to rCD40L over 14 days of culture in comparable amounts to NIH3T3/tCD40L. B-cell division in response to CD40L was also confirmed by carboxyfluorescein succinimidyl ester dilution. Moreover, rCD40L induced on B cells upregulation of co-stimulatory molecules essential for antigen presentation. Additionally, proliferation of T cells from allogeneic healthy volunteers confirmed the immunostimulatory capacities of CD40-activated B cells.

Conclusions: We demonstrated that B cells with potent antigen presentation capacity can be generated and expanded by use of a non-xenogeneic form of CD40L that could be implemented in future human clinical settings.