TELOMERASE ACTIVATION IN NORMAL B-LYMPHOCYTES AND NON-HODGKINS-LYMPHOMAS

Activation of telomerase seems to be a prerequisite for immortalizatio n and is found in permanent cell lines and most malignant tumors, Norm al somatic cells are generally telomerase negative, except for bone ma rrow stem cells, Weak activity is also present in peripheral blood cel ls. In the present study strong telomerase activity was demonstrated i n vivo in normal mature cells of the immune system, as well as in mali gnant lymphomas. Benign lymph nodes had lower telomerase activity than benign tonsils, which exhibited intermediate to high activity compara ble with findings in malignant lymphomas, In benign tonsils the activi ty seemed to be restricted to germinal center B cells. In benign lymph oid tissues telomerase activity correlated with B-cell numbers and cel l proliferation, but this was not observed in the lymphoma group. High -grade lymphomas exhibited higher levels of telomerase compared with l ow-grade cases. The data showed that in vivo activation of telomerase is a characteristic feature of germinal center B cells. Different sign als for activation of telomerase are likely to exist, one of them bein g immune stimulation. The data suggest that telomerase activity in mal ignant lymphomas can be explained by an ''induction and retention'' mo del, ie, transformation occurs in a normal, mature B cell with reactiv ated telomerase, which is retained in the neoplastic clone. (C) 1996 b y The American Society of Hematology.