In an effort to understand the mechanisms involved in the protective immunity to malarial sporozoites, an A/J mouse/Plasmodium berghei model was studied. Protective immunity could consistently be adoptively transferred only by using sublethal irradiation of recipients (500 R); a spleen equivalent (100 × 106) of donor cells from immune syngeneic mice; and a small booster immunization (1 × 104) of recipients with irradiation-attenuated sporozoites. Recipient animals treated in this manner were protected from lethal challenge with 1 × 104 nonattenuated sporozoites. Immune and nonimmune serum and spleen cells from nonimmune animals did not protect recipient mice. Fewer immune spleen cells (50 × 106) protected some recipients. In vitro treatment of immune spleen cells with anti-ϑ sera and complement abolished their ability to transfer protection. This preliminary study suggests that protective sporozoite immunity can be transferred with cells, and that it is T cell dependent.

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This work was supported by the Naval Medical Research and Development Command, Work Unit No. MR021.05.01.0041. The opinions or assertions contained herein are the private ones of the authors and are not to be construed as official or reflecting the views of the Navy Department or the naval service at large. The experiments reported herein were conducted according to the principles set forth in the “Guide for the Care and Use of Laboratory Animals,” Institute of Laboratory Animal Resources, National Research Council, Department of Health, Education and Welfare Publication No. (NIH) 74-23.

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