Influence of TNFα on normal bone marrow progenitors. Fresh CD34⁺ were cultured in medium containing various cytokines as described in “Materials and methods” in the presence or absence of TNFα (20 ng/mL) for 7 to 14 days. (A) Viable cells were counted by trypan blue dye exclusion. Results represent the mean ± SD of 5 independent experiments. ^***P < .001. (B) Differentiation was analyzed by flow cytometry using anti-CD34 monoclonal antibody at 7 days of culture. Results are representative of 3 independent experiments. (C) Transcripts of hTERT were quantified using the LightCycler TeloTAGGGhTERT quantification kit as described in “Materials and methods.” hTERT/PBGD represents the ratio between hTERT and PBGD transcripts normalized to untreated control cells at 7 days of culture. They are expressed as the mean hTERT/PBGD values from 3 independent experiments ± SDs; ^****P < .001. (D) Telomerase activity was measured by using the TeloTAGGG telomerase PCR ELISA kit as described in “Materials and methods.” Results are expressed as mean RTA values ± SDs of 3 independent experiments. ^*P = .014; ^**P = .002 and .004.