Fig. 2.

Proliferation and differentiation of B cells from CSR-deficient patients upon activation. The capacity of B cells from healthy adult controls, healthy cord bloods, and CD40L-, AID-, and UNG-deficient CSR patients to proliferate and differentiate in vitro were tested. CFSE-labeled PBMCs were cultured for 6 days, normalized for B cell numbers (1 × 10⁵ B cells/well). T cell-independent B cell activation was tested with CpG in the presence of IL-2. T cell-dependent B cell stimulation was mimicked by the combinations of αIgM/αCD40/IL-21. Effect of T cell stimulation was mimicked by αCD3/αCD28 stimulation, targeting T cells specifically. Representative FACS plots are shown of B cell subset distribution after 6 days of culture in the presence of the indicated stimuli. Gated on CD19⁺ lymphocytes to show CFSE dilution indicating proliferation after 6 days of culture, and to demonstrate the emergence of the subsets of Ig-producing B cells, i.e., plasmablasts and/or plasmacells (sIgD⁻/CD27⁺⁺/CD38⁺⁺)