ANTIGEN-INDEPENDENT ACTIVATION OF NAIVE AND MEMORY RESTING T-CELLS BYA CYTOKINE COMBINATION

We investigated whether human resting T cells could be activated to pr oliferate and display effector function in the absence of T cell recep tor occupancy. We report that combination of interleukin 2 (IL-2), tum or necrosis factor alpha, and IL-6 activated highly purified naive (CD 45RA(+)) and memory (CD45RO(+)) resting CD4(+) T cells to proliferate. Under this condition, memory resting T cells could also display effec tor function as measured by lymphokine synthesis and help for immunogl obulin production by B cells. This novel Ag-independent pathway of T c ell activation may play an important role in vivo in recruiting effect or T cells at the site of immune response and in maintaining the clona l size of memory T cells in the absence of antigenic stimulation. More over, cytokines can induce proliferation of naive T cells without swit ch to memory phenotype and this may help the maintenance of the periph eral pool of naive T cells.