DISTRIBUTION OF SERINE ESTERASE-ACTIVITY IN THE LYMPHOID SYSTEM OF C57BL/6 MICE, EFFECT OF AGING ON THE ENZYMATIC-ACTIVITY

1. The activity of serine esterase (SE) was investigated in the lymphoid system of C57BL/6 mice. SE activity increased in the lymphoid tissues with their content of mature T-lymphocytes, except that high levels were also observed in various populations of bone marrow cells. 2. The maturation of T-lymphocytes in the thymus was accompanied by an increase in their SE activity. 3. Experiments on the influence of age on SE activity showed that while thymocytes were not affected, a three-fold increase in activity occurs in spleen lymphocytes between the ages of 26 and 78 wk.