Immunological changes in the lymphocyte population with increasing age

: The lymphocytes of the peripheral blood of 90 clinically healthy persons aged between 9 months and 90 years have been investigated. Children up to the age of 10 showed the highest amount of absolute lymphocytes. The number of lymphocytes decreased continually with the test subject's increasing age. Persons between 80 and 90 years of age had the lowest counts. The reduction in old age in the number of lymphocytes as a whole is attributed to a significant drop in T-lymphocytes. On the other hand, the proportion of B-cells remains at an almost constant level in all age groups. The reduction of lymphocytes as a whole, as well as that of the absolute T-cells, are discussed as possible causes of impaired cellular immunity in old age.