B and T lymphocytes in man. IV. Circulating B, T and "null" lymphocytes in aging population.

T, B and "Null" lymphocytes were determined in the peripheral blood of 98 adults, 26 of them were between 20 to 40 years of age and 72 between 60 to 96 years of age. The total number of lymphocytes were about the same in both groups. The percent and absolute number of T cells decreased significantly in the aged. Although the percent of B lymphocytes increased with age, the absolute number of B lymphocytes remained about the same.