Investigations on the age-dependence of T-lymphocyte subpopulations and lymphocyte reactivity.

The percentage T-lymphocyte subpopulations were determined with the aid of radioactively-labelled monoclonal antibodies to the antigens of total T-lymphocytes and to suppressor T-lymphocyte surface antigens and the responsiveness of the lymphocytes in the presence of ConA and PHA was investigated in groups of 8 subjects aged either between 20 and 30 years or over 75 years. It was found that there was no difference with respect to the response of the lymphocytes to the plant mitogens ConA and PHA. The percentage of suppressor T-lymphocytes, on the other hand, was significantly reduced in the older subjects, whilst the percentage of total T-lymphocytes did not differ significantly from the percentage in younger subjects. These results are discussed in connection with published data.