Requirement for Continuous Antigenic Stimulation of Immune Spleen Cells in Adoptive Transfer of Cell-Mediated Protection against Tularemia,

Abstract : Under appropriate conditions passively transferred spleen cells from AKR/J mice immunized with live Francisella tularensis confer high-grade protection (survival approaching 100%) to nonimmune syngeneic recipients against intravenous, intraperitoneal, or subcutaneous challenge with a fully virulent strain. When experimental conditions were adjusted to eliminate viable cell-associated F. tularensis, adoptive immunity was abrogated. However, concurrent administration of appropriate concentrations of homologous killed organisms and immunocompetent spleen cells devoid of viable organisms provided conditions for restoration or enhancement of protective activity; recipients treated in this manner were resistant to infection for at least 47 days. Short-term nonspecific protection against intraperitoneal but not against subcutaneous challenge was elicited by injection of immune cell recipients with appropriate concentrations of killed organisms from taxonomically unrelated genera. In this model system, complicating effects introduced by transfer of replicating organisms have been eliminated and survival can be used to evaluate protection.