Age-related changes in B and T lymphocytes and decline of humoral immune responsiveness in aged mice.

The activity of the immune system declines in an age-related fashion, after reaching a peak in young-adult animals. Although this pattern has been well documented, the mechanisms responsible for the decline of immune potential in senescence have not been fully elucidated. At the same time, it has become apparent that the immune response depends on complex interactions among different cell types. We review the results of the analyses of B- and T-lymphocyte function and activity in the humoral responsiveness of aged mice that have been performed in a number of laboratories, with a variety of experimental techniques. We conclude that an increase in T-cell suppressor function is the first immunologic lesion of aging in mice. This is followed by a decrease in T-cell helper function and finally by a loss of B-cell function.