Impairment of replicating DNA ends by normal DNA polymerases and the gradual shrink of the ends of linear chromosomes (telomeres) is recently considered to play a role for the limited growth of cells. Telomerase activity, that uses an RNA template to extend telomeric DNA, appears in the malignant transformation of human cells. Freshly isolated normal lymphoid cells do not express any detectable telomerase activity. Interestingly, anti-CD3 monoclonal antibody (mAb) induces telomerase activity in human peripheral T cells. Ca ionophore and phorbol 12, 13-dibutyrate (PDB), which are considered as the stimulants that bypass T cell receptor (TCR) signaling, also induce telomerase activity. These results clearly demonstrate that telomerase activity appears in normal lymphoid cells and suggest that antigen receptor-mediated induction of telomerase activity is playing a role in the proliferation of human T cells in the immune response. (C) 1996 Academic Press, Inc.
