DIFFERENTIAL AGE-CHANGE IN THE NUMBERS OF CD4-CELL SUBSETS IN HUMAN PERIPHERAL-BLOOD(CD45RA+ AND CD4+CD29+ T)

Peripheral blood mononuclear cells were obtained from people ranging i n age from newborn to 102 years old and analyzed by dual color flow cy tometer in terms of number and percentage of various subsets of T cell s, B cells and natural killer cells (CD3, 4, 5, 8, 11b, 19, 20, 21, 25 , 29, 45RA and 56). Numbers of T cells (CD3+ or CD5+ cells) significan tly declined at the 3rd decade as compared with those of younger peopl e, stayed at a relatively constant level between the 3rd and the 7th d ecade and gradually declined thereafter. In T cell subsets, both CD4 a nd CD8 positive cells decreased with age, but a decrease was more pron ounced in the latter, showing an age-related increase of CD4/CD8 ratio . The most interesting finding was a contrasting age-change in two sub sets of CD4+ T cells; i.e. a subset of suppressor inducer T cells (CD4 + CD45RA+ naive cells) decreased with age, while a subset of helper in ducer T cells (CD4+ CD29+ memory cells) increased with age. CD20+ B ce lls also decreased with age in a manner similar to that observed in T cells. Natural killer cells (CD56) showed an increase in numbers with age. The relationship between these changes in various subsets of peri pheral blood leukocytes and the age-related decline in immune function s has been discussed.