Antigen-specific, interleukin 2-propagated T lymphocytes confer resistance to a murine malarial parasite, Plasmodium chabaudi adami.

To explore cell-mediated immune mechanisms in host defense against malaria, we utilized a murine model system in which antibody-independent mechanisms of immunity are known to play a major role. Splenic T lymphocytes obtained from Plasmodium chabaudi adami-immune mice were maintained in vitro by using IL 2-containing medium and frequent antigenic stimulation. These IL 2-propagated T lymphocytes were characterized for their antigen reactivity, surface phenotype, and ability to confer protection to P. chabaudi adami in reconstituted mice. IL 2-dependent T lymphocytes maintained their capacity to proliferate in vitro to solubilized parasite preparations of homologous but not heterologous antigens. Antigen-specific proliferation was H-2 restricted, requiring antigen-presenting cells of the correct haplotype. More importantly, these propagated T lymphocytes were effective in adoptively transferring protection to both athymic nude mice and sublethally irradiated recipients. The protective response was dose dependent and antigen specific, because recipients resisted challenge infection with P. chabaudi adami but not with the heterologous parasite Plasmodium yoelii 17X. Pretreatment of the IL 2-propagated cells with anti-Thy-1.2 and complement abrogated their ability to transfer protection. Collectively, these results suggest that T lymphocytes obtained from P. chabaudi adami-immune mice, propagated and expanded in vitro, retain antigen specificity and passive protective activity in vivo.