ALLOANTIGEN PRIMING INDUCES A STATE OF UNRESPONSIVENESS IN HUMAN UMBILICAL-CORD BLOOD T-CELLS

Induction of alloreactivity in human adult and umbilical cord blood T cells was evaluated in mixed leukocyte culture by exposure to an allog eneic lymphoblastoid line that expresses known costimulatory molecules . Initial exposure to alloantigen-presenting cells (allo-APC) induced strong proliferative responses in both adult and cord blood T cells, H owever, in contrast to adult T cells, cord blood T cells exhibited lit tle proliferation after restimulation with donor APC, Primed cord bloo d T cells could respond to interleukin 2 (IL-2), but unresponsiveness to alloantigen was not overcome by addition of exogenous IL-2, Unrespo nsiveness was long-lasting and appeared to be maintained by a combinat ion of induction of anergy and activity of CD8(+) suppressor cells. Th is information may contribute to use of human cord blood as an allogen eic source of transplantable stem cells.