Age-related variation in lymphocyte subpopulations.

Peripheral blood lymphocytes are heterogeneous and can be divided into subpopulations based on cell surface markers. Lymphocytes from 101 normal individuals of all ages were tested for their ability to form spontaneous rosettes with sheep erythrocytes (T cells) and for surface immunoglobulins (B cells). Cord bloods of newborn infants and bloods from children (age 1-10 years) showed greater numbers of total lymphocytes, total T cells and unmarked cells than a control group of 50 individuals from age 11-60 years. In 22 normal elderly individuals (age 61-98 years), total lymphocytes and total T and B cells were not decreased. These data suggest that the depression of cellular immune response described in elderly populations may be related to a dysfunction in a segment of T cells or an aberration in the complex interaction among T cells, B cells and macrophages.