Induction of telomerase activity in B cells of tonsils and PBLs. (A) Tonsillar B cells were stimulated with either biotin-labeled mouse antihuman IgM MoAb (10 μg/mL) or biotin-labeled mouse antihuman IgD MoAb (10 μg/mL) in combination with anti-CD40 MoAb (10 μg/mL). Streptavidin (20 μg/mL) was used for the hypercross-linkage of BCR. (B) B cells of tonsils and PBLs from the same donor were stimulated for 2 days with the various stimulatory reagents indicated. After stimulation, TRAP assay was conducted.