Age-related changes in ConA- and LPS-induced lymphocyte transformation. I. Effect of culture conditions on mitogen responses of blood and spleen lymphocytes from young and aged rats.

Age-related changes in LPS- and ConA-responsiveness of rat spleen lymphocytes as judged by 14C-TdR incorporation were studied. It was found that responses to both mitogens decreased with advancing age. This report shows that the reduced 14C-TdR incorporation could not be attributed to decreased cell survival or viability of spleen lymphocytes from old rats, to delayed proliferation of the old lymphocytes, or to differences in minimum mitogen doses required for optimal stimulation. The results suggest that the observed decrease is due to a decrease in the number of mitogen responsive cells. The response to LPS was even more depressed than was the response to ConA. The response to ConA in whole blood is also shown to decline with ageing at multiple mitogen doses.