Figure 1.

hTERT mRNA expression and telomerase activity in tonsil and peripheral-blood B cells. (A) Representative Northern blots of hTERT expression in naïve, GC, and memory B cells isolated from human tonsils, resting B cells isolated from peripheral blood, and cultured fibroblasts from neonatal foreskin are shown. The blots were probed sequentially with hTERT and GAPDH probes. (B) The relative abundance of hTERT mRNA and telomerase activity in B cell subsets. The hTERT level from each cell subset shown in A was analyzed by phosphorimager and imagequant software. The relative abundance of hTERT mRNA was normalized on the basis of cell equivalents. The open bars represent the relative abundance of hTERT expression for each cell subset. The level of hTERT in naïve cells was arbitrarily set at 1. Telomerase activity was measured by a modified TRAP assay from ≈10⁴ cells, and the results were normalized on the basis of cell equivalents. The black bars represent the relative levels of telomerase activity. The level of telomerase in naïve cells was arbitrarily set at 1. (C) hTERT mRNA expression in tonsil section by in situ hybridization. The tonsil sections were probed with sense (C, A) and antisense probe (C, B). Strong expression of hTERT is observed in GC cells but not in surrounding naïve and memory B cells.