The effect of age on antigen-sensitive cells.

The primary humoral immune response to heterologous red cell antigens declines in mice after 12 months of age. The cellular response to histocompatibility antigens of lymph node lymphocytes from mice 3 months and 12 to 27 months old are evaluated in these studies. It was found that lymphocytes from aged mice are as able to transform into large pyroninophilic cells and proliferate after exposure to antigen as lymphocytes from 3- to 4-month-old mice. However, results of cellular responses of intermediate age groups suggest that the cells that respond to antigen in the old mice may be a different population of lymphocytes from the cells that respond in the young mice.