T-lymphocyte long-term cultures have a constant histone variant pattern during aging

Human peripheral long-term T-lymphocyte cell cultures show some characteris tics similar to those of fibroblast cell lines, the latter of which have be en used as in vitro systems for cellular aging studies for many years. Both show a limited in vitro life span, as well as a progressive prolongation o f their cell cycle with increasing age. However, whereas T-cell cultures di e from apoptosis at the end of their proliferative capacity, fibroblasts ca n be maintained for long periods of time in stationary cultures as postmito tic senescent cells. Previous studies analyzing the histone variant pattern of a human lung embryonic fibroblast cell line have shown that this patter n changes as a function of cumulative population doublings in a manner not unlike that found in terminally differentiating systems. In the present stu dy the histone variant composition of long-term T-cell cultures was analyze d as a function of population doublings and compared to a human diploid fib roblast system. The results from this study provide a distinction at the mo lecular level among these two in vitro aging model systems, because it was found that long-term T-cell cultures show a constant histone variant consti tution throughout their in vitro life, dissimilar to previous findings usin g the fibroblast cell system. (C) 1999 Elsevier Science Inc. All rights res erved.