Optimization of human B cell culture conditions for expansion of activated or differentiated B cells

In vitro B cell cutures are important for fundamental and applied science: these can be used to study antigenic specificity of B and T cells, as well as to produce monoclonal antibodies and other biopharmaceuticals. That is why the development of an optimal protocol for culturing of activated B cells, antibody-secreting cells (ASCs), and germinal center (GC) B cells in vitro remains an urgent task. The study aimed to find the conditions ensuring the following: high B cell expansion and survival rates, ASC accumulation, GC B cell production and accumulation. For that the CD27‒ and/or CD27+ B cells from human peripheral blood were cultured in the presence of the feeder 3T3-hCD40L line, various combinations of cytokines (IL21, IL4, BAFF), human serum components or under the control conditions throughout 7 days. Flow cytometry analysis of B cell cultures showed that the CD40L and IL21 co-existence was essential for achieving high B cell expansion, survival, and differentiation with the production of the CD27highCD38high ASCs and CD95highBcl-6+ GC-like cells. The highest expansion was observed in the cultures of CD27 naïve cells in the presence of human serum components. The IL4 supplementation moderately increased the share of GC-like cells. The maximum ASC accumulation was observed in the cultures of CD27+ memory В cells. The approach developed made it possible to find the optimal conditions for in vitro B cell culturing and clearly demonstrated the impact of both individual IL-21, IL-4, BAFF cytokines and their combinations on the B cell cultures of various subpopulations.