The activity of gamma-glutamyl transpeptidase (gamma-GT) in populations of mononuclear cells from human peripheral blood.

The activity of gamma-glutamyl transpeptidase (EC 2.3.2.2) was observed in populations of non-stimulated mononuclear cells of human peripheral blood selected with antibody-coated magnetic particles. The highest activities of gamma-GT were found in monocytes (7.3-20.0 pkat/10(6) cells). The examination of T lymphocytes revealed a significant difference between CD4-positive (4.1 pkat/10(6) cells) and CD8-positive cells (1.2 pkat/10(6) cells). B lymphocytes and NK cells showed the lowest activities of 0.3 and 1.3 pkat/10(6) cells, respectively. The obvious differences in gamma-GT activities demonstrated here may reflect different biochemical capacities of these cell types, related to their distinct functions in the immune system.