Utilization of antigen specific cytotoxic T-cells as a sensitive approach to investigate the fate of placentally injected allogeneic lymphocytes

In this report we present a model for the introduction of immunocompetent populations during murine gestation and the subsequent detection of allogeneic cells in the offspring. A highly sensitive in vitro assay, the primed lymphocyte cytotoxicity assay, which can detect extremely low numbers of allogeneic cells residing within host tissue is described. Primed cytotoxic T cells specific for class I antigens were found to be restimulated by as few as 10-50 allogeneic spleen cells from within 10 000 syngeneic neonatal spleen or liver cells. Various tissues derived from neonatal mice which had been placentally injected 1 or 10 days previously were found to contain markedly different percentages of "chimeric" cells in the neonatal organs examined. Notably, while spleen and lung contained more allogeneic cells early following injection, 10 days later the liver contained the highest percentage and the thymus and spleen a significantly lower percentage of allogeneic cells. These findings are discussed with respect to the possible enhancement or depression of the offspring's immune responsiveness following interaction with alloantigen bearing lymphoid cells.