CD4 and infection: The results obtained with CD4+ T cells were similar to those obtained with PBL: (i) basal telomerase activity was detected in CD4+ T cells from non infected chickens (67527), (ii) a slight induction of telomerase activity was first observed at 7 days (71750), corresponding to the phase of primary semi-productive infection (iii), this induction peaked at 14 days p.i. (107800), corresponding to the expected time of lymphoma onset and (iv) persisted until 28 days p.i. (135310).