Intracellular TLR-9 correlates with proliferation following CpG DNA stimulation for both naive (CD27⁻) and memory (CD27⁺) B cells. Intracytoplasmic TLR-9 was measured by flow cytometry immediately after isolating naive and memory B cells (shaded histogram) for both populations. The bar represents the isotype control measurement. Simultaneous intracytoplasmic TLR-9 and CFSE measurements were obtained following CpG DNA stimulation in the presence of IL-2, IL-10, and IL-15 at the time intervals listed for each population. Both cell types expressed a basal level of intracytoplasmic TLR-9, while memory B cells had a faster increase in intracytoplasmic levels than their CD27⁻ counterparts. Results are representative of 7 independent experiments from different blood donors.