The Response Pattern of Human T Cells to Stimulation Following Expansion in IL-2

Abstract

The ability to stimulate and induce responses of T cells is influenced by their age and state of differentiation. We have examined the response upon restimulation of T cells expanded in IL-2. Our results demonstrate that large numbers of T cells, which after activation react by secreting IL-2, can be obtained from small numbers of PBL. In this study T cells were grown in IL-2 and, after 12–14 days, IL-2 was withdrawn in order to deprive them of growth factors. Our findings showed that after resting for 48 hours without IL-2, IL-2- dependent cells reverted to small lymphocytes, ceased to incorporate ³H-TdR, and had no mRNA for activation antigens such as Tac or IL-2. The cells could be reactivated to proliferate by stimulation with a calcium ionophore ionomycin and phorbol dibutyrate (PdB). Cells from insulin dependent diabetes mellitus patients with a defined immunoregulatory defect were then studied. Our results demonstrated that the IL-2 expanded cells evidenced the immunoregulatory defect for IL-2 synthesis that we had initially defined using virgin T cells from peripheral blood. These results demonstrate that studies of immune function can be undertaken in donors from whom limited numbers of peripheral blood lymphocytes are available using primed cells which have been allowed to dedifferentiate.