Adoptive CD8 T cell control of pathogens cannot be improved by combining protective epitope specificities

Adoptive transfer of CD8T cells has the potential to cure infectious or malignant diseases that are refractory to conventional chemotherapy. A practically important but still unanswered question is whether mixtures of protective CD8T cells with different epitope specificities mediate more efficient effector cell functions than do the monospecific individual CD8T cell populations. In this study, we have addressed this issue for models of viral and bacterial infection. CD8T cell-mediated cytotoxicity in vitro and protection in vivo were assessed to test whether CD8T cell lines cooperate in target cell lysis and control of infection, respectively. Our data clearly show that mixtures of cytolytic T cell lines specific for different epitopes of either murine cytomegalovirus or Listeria monocytogenes do not act synergistically. An efficient anti-infectious protection thus proved to be dependent primarily on the number of transferred protective CD8T cells rather than on the cooperative effects of multiple specificities.